fix recently committed typos by msaitoh in few more places, as well as few more.
mainly s/contigous/contiguous/ and s/miliseconds/milliseconds/ in comments.

s/threshhold/threshold

branches: 1.27.12;
All of snd_wnd, snd_cwnd and snd_ssthresh in stuct tcpcb are u_long,
so use u_long and ulmin() instead of u_int and uimin(). Found by lgtm bot.

XXX TCP's sequence number is uint32_t, so it might be good to change some
entries in struct tcpcb to uint32_t instead of u_long. FreeBSD did it.

Rename min/max -> uimin/uimax for better honesty.

These functions are defined on unsigned int. The generic name
min/max should not silently truncate to 32 bits on 64-bit systems.
This is purely a name change -- no functional change intended.

HOWEVER! Some subsystems have

#define min(a, b) ((a) < (b) ? (a) : (b))
#define max(a, b) ((a) > (b) ? (a) : (b))

even though our standard name for that is MIN/MAX. Although these
may invite multiple evaluation bugs, these do _not_ cause integer
truncation.

To avoid `fixing' these cases, I first changed the name in libkern,
and then compile-tested every file where min/max occurred in order to
confirm that it failed -- and thus confirm that nothing shadowed
min/max -- before changing it.

I have left a handful of bootloaders that are too annoying to
compile-test, and some dead code:

cobalt ews4800mips hp300 hppa ia64 luna68k vax
acorn32/if_ie.c (not included in any kernels)
macppc/if_gm.c (superseded by gem(4))

It should be easy to fix the fallout once identified -- this way of
doing things fails safe, and the goal here, after all, is to _avoid_
silent integer truncations, not introduce them.

Maybe one day we can reintroduce min/max as type-generic things that
never silently truncate. But we should avoid doing that for a while,
so that existing code has a chance to be detected by the compiler for
conversion to uimin/uimax without changing the semantics until we can
properly audit it all. (Who knows, maybe in some cases integer
truncation is actually intended!)

branches: 1.25.2;
Remove now unused tcpip.h includes. Some were already unused before.

Remove #ifdef INET. Same as tcp_input.c. Makes the code easier to
understand.

Also make tcp6_mtudisc() static in tcp_subr.c.

branches: 1.23.14;
Restore behaviour to pre- tcp_congctl.c:1.18 for SACK. Further analysis
of the change is required.

OK kefren@

PR/51753 tcp SACK causes SSH disconnect

Remove unnecessary inclusions of nd6.h

branches: 1.21.2;
Sweep unnecessary route.h inclusions

sprinkle _KERNEL_OPT

branches: 1.19.4; 1.19.6; 1.19.8; 1.19.10;
Cubic changes:
* correct W(t) calculation
* check wmax limits
* change W_max in slow and fast retransmit
* correct rtt approximation
Reno:
* move comment I forgot behind after fast_retransmit() split

* implement TCP CUBIC congestion control algorithm
* move tcp_sack_newack bits inside reno and newreno_fast_retransmit_newack
* notify ECN peer about cwnd shrink in [new]reno_slow_retransmit

Based on the patch proposed on tech-net@ on Nov 7 with minor improvments:
* adapt wmax for no-fast convergence case
* correct cbrt calculation for big window sizes (>750KB)

Mark a diagnostic-only variable

branches: 1.16.4; 1.16.14; 1.16.18;
simplify code a little. no functional changes.

branches: 1.15.22; 1.15.28;
Remove clause 3 and 4 from TNF licenses

branches: 1.14.2; 1.14.4;
Rework tcp congctl selection code so that the congctl entries can be const.
Don't access tcp_congctl stuff outside of tcp_congctl.c, use routines to
update t_congctl. This code is slightly now more complicated.

branches: 1.13.8; 1.13.24; 1.13.28;
Replace a simple lock with a mutex and make it static.

branches: 1.12.2; 1.12.6; 1.12.12;
__unused removal on arguments; approved by core.

branches: 1.11.2;
constify.

tcp_reno_newack: remove an __unused because it's now used.

tcp_reno_newack: regardless of sysctl setting, use L=1*SMSS when
we are doing retransmission.

implement RFC3465 appropriate byte counting.
from Kentaro A. Kurahone, with minor adjustments by me.
the ack prediction part of the original patch was omitted because
it's a separate change. reviewed by Rui Paulo.

Move comments to proper places.

Add a new tcp_congctl(9) structure member for congestion experienced callback.
Needed by HSTCP.

- sprinkle __unused on function decls.
- fix a couple of unused bugs
- no more -Wno-unused for i386

tcp_reno_newack(): bring the exact original code.
tcp_newreno_newack(): call tcp_reno_newack() if partialacks < 0.

tcp_reno_newack/tcp_newreno_newack: remove stale comments.

tcp_newreno_newack: actually inflate cwnd as it used to do.

Modular (I tried ;-) TCP congestion control API. Whenever certain conditions
happen in the TCP stack, this interface calls the specified callback to
handle the situation according to the currently selected congestion
control algorithm.
A new sysctl node was created: net.inet.tcp.congctl.{available,selected}
with obvious meanings.
The old net.inet.tcp.newreno MIB was removed.
The API is discussed in tcp_congctl(9).

In the near future, it will be possible to selected a congestion control
algorithm on a per-socket basis.

Discussed on tech-net and reviewed by <yamt>.

s/threshhold/threshold

All of snd_wnd, snd_cwnd and snd_ssthresh in stuct tcpcb are u_long,
so use u_long and ulmin() instead of u_int and uimin(). Found by lgtm bot.

XXX TCP's sequence number is uint32_t, so it might be good to change some
entries in struct tcpcb to uint32_t instead of u_long. FreeBSD did it.

Rename min/max -> uimin/uimax for better honesty.

These functions are defined on unsigned int. The generic name
min/max should not silently truncate to 32 bits on 64-bit systems.
This is purely a name change -- no functional change intended.

HOWEVER! Some subsystems have

#define min(a, b) ((a) < (b) ? (a) : (b))
#define max(a, b) ((a) > (b) ? (a) : (b))

even though our standard name for that is MIN/MAX. Although these
may invite multiple evaluation bugs, these do _not_ cause integer
truncation.

To avoid `fixing' these cases, I first changed the name in libkern,
and then compile-tested every file where min/max occurred in order to
confirm that it failed -- and thus confirm that nothing shadowed
min/max -- before changing it.

I have left a handful of bootloaders that are too annoying to
compile-test, and some dead code:

cobalt ews4800mips hp300 hppa ia64 luna68k vax
acorn32/if_ie.c (not included in any kernels)
macppc/if_gm.c (superseded by gem(4))

It should be easy to fix the fallout once identified -- this way of
doing things fails safe, and the goal here, after all, is to _avoid_
silent integer truncations, not introduce them.

Maybe one day we can reintroduce min/max as type-generic things that
never silently truncate. But we should avoid doing that for a while,
so that existing code has a chance to be detected by the compiler for
conversion to uimin/uimax without changing the semantics until we can
properly audit it all. (Who knows, maybe in some cases integer
truncation is actually intended!)

branches: 1.25.2;
Remove now unused tcpip.h includes. Some were already unused before.

Remove #ifdef INET. Same as tcp_input.c. Makes the code easier to
understand.

Also make tcp6_mtudisc() static in tcp_subr.c.

branches: 1.23.14;
Restore behaviour to pre- tcp_congctl.c:1.18 for SACK. Further analysis
of the change is required.

OK kefren@

PR/51753 tcp SACK causes SSH disconnect

Remove unnecessary inclusions of nd6.h

branches: 1.21.2;
Sweep unnecessary route.h inclusions

sprinkle _KERNEL_OPT

branches: 1.19.4; 1.19.6; 1.19.8; 1.19.10;
Cubic changes:
* correct W(t) calculation
* check wmax limits
* change W_max in slow and fast retransmit
* correct rtt approximation
Reno:
* move comment I forgot behind after fast_retransmit() split

* implement TCP CUBIC congestion control algorithm
* move tcp_sack_newack bits inside reno and newreno_fast_retransmit_newack
* notify ECN peer about cwnd shrink in [new]reno_slow_retransmit

Based on the patch proposed on tech-net@ on Nov 7 with minor improvments:
* adapt wmax for no-fast convergence case
* correct cbrt calculation for big window sizes (>750KB)

Mark a diagnostic-only variable

branches: 1.16.4; 1.16.14; 1.16.18;
simplify code a little. no functional changes.

branches: 1.15.22; 1.15.28;
Remove clause 3 and 4 from TNF licenses

branches: 1.14.2; 1.14.4;
Rework tcp congctl selection code so that the congctl entries can be const.
Don't access tcp_congctl stuff outside of tcp_congctl.c, use routines to
update t_congctl. This code is slightly now more complicated.

branches: 1.13.8; 1.13.24; 1.13.28;
Replace a simple lock with a mutex and make it static.

branches: 1.12.2; 1.12.6; 1.12.12;
__unused removal on arguments; approved by core.

branches: 1.11.2;
constify.

tcp_reno_newack: remove an __unused because it's now used.

tcp_reno_newack: regardless of sysctl setting, use L=1*SMSS when
we are doing retransmission.

implement RFC3465 appropriate byte counting.
from Kentaro A. Kurahone, with minor adjustments by me.
the ack prediction part of the original patch was omitted because
it's a separate change. reviewed by Rui Paulo.

Move comments to proper places.

Add a new tcp_congctl(9) structure member for congestion experienced callback.
Needed by HSTCP.

- sprinkle __unused on function decls.
- fix a couple of unused bugs
- no more -Wno-unused for i386

tcp_reno_newack(): bring the exact original code.
tcp_newreno_newack(): call tcp_reno_newack() if partialacks < 0.

tcp_reno_newack/tcp_newreno_newack: remove stale comments.

tcp_newreno_newack: actually inflate cwnd as it used to do.

Modular (I tried ;-) TCP congestion control API. Whenever certain conditions
happen in the TCP stack, this interface calls the specified callback to
handle the situation according to the currently selected congestion
control algorithm.
A new sysctl node was created: net.inet.tcp.congctl.{available,selected}
with obvious meanings.
The old net.inet.tcp.newreno MIB was removed.
The API is discussed in tcp_congctl(9).

In the near future, it will be possible to selected a congestion control
algorithm on a per-socket basis.

Discussed on tech-net and reviewed by <yamt>.

All of snd_wnd, snd_cwnd and snd_ssthresh in stuct tcpcb are u_long,
so use u_long and ulmin() instead of u_int and uimin(). Found by lgtm bot.

XXX TCP's sequence number is uint32_t, so it might be good to change some
entries in struct tcpcb to uint32_t instead of u_long. FreeBSD did it.

Rename min/max -> uimin/uimax for better honesty.

These functions are defined on unsigned int. The generic name
min/max should not silently truncate to 32 bits on 64-bit systems.
This is purely a name change -- no functional change intended.

HOWEVER! Some subsystems have

#define min(a, b) ((a) < (b) ? (a) : (b))
#define max(a, b) ((a) > (b) ? (a) : (b))

even though our standard name for that is MIN/MAX. Although these
may invite multiple evaluation bugs, these do _not_ cause integer
truncation.

To avoid `fixing' these cases, I first changed the name in libkern,
and then compile-tested every file where min/max occurred in order to
confirm that it failed -- and thus confirm that nothing shadowed
min/max -- before changing it.

I have left a handful of bootloaders that are too annoying to
compile-test, and some dead code:

cobalt ews4800mips hp300 hppa ia64 luna68k vax
acorn32/if_ie.c (not included in any kernels)
macppc/if_gm.c (superseded by gem(4))

It should be easy to fix the fallout once identified -- this way of
doing things fails safe, and the goal here, after all, is to _avoid_
silent integer truncations, not introduce them.

Maybe one day we can reintroduce min/max as type-generic things that
never silently truncate. But we should avoid doing that for a while,
so that existing code has a chance to be detected by the compiler for
conversion to uimin/uimax without changing the semantics until we can
properly audit it all. (Who knows, maybe in some cases integer
truncation is actually intended!)

branches: 1.25.2;
Remove now unused tcpip.h includes. Some were already unused before.

Remove #ifdef INET. Same as tcp_input.c. Makes the code easier to
understand.

Also make tcp6_mtudisc() static in tcp_subr.c.

branches: 1.23.14;
Restore behaviour to pre- tcp_congctl.c:1.18 for SACK. Further analysis
of the change is required.

OK kefren@

PR/51753 tcp SACK causes SSH disconnect

Remove unnecessary inclusions of nd6.h

branches: 1.21.2;
Sweep unnecessary route.h inclusions

sprinkle _KERNEL_OPT

branches: 1.19.4; 1.19.6; 1.19.8; 1.19.10;
Cubic changes:
* correct W(t) calculation
* check wmax limits
* change W_max in slow and fast retransmit
* correct rtt approximation
Reno:
* move comment I forgot behind after fast_retransmit() split

* implement TCP CUBIC congestion control algorithm
* move tcp_sack_newack bits inside reno and newreno_fast_retransmit_newack
* notify ECN peer about cwnd shrink in [new]reno_slow_retransmit

Based on the patch proposed on tech-net@ on Nov 7 with minor improvments:
* adapt wmax for no-fast convergence case
* correct cbrt calculation for big window sizes (>750KB)

Mark a diagnostic-only variable

branches: 1.16.4; 1.16.14; 1.16.18;
simplify code a little. no functional changes.

branches: 1.15.22; 1.15.28;
Remove clause 3 and 4 from TNF licenses

branches: 1.14.2; 1.14.4;
Rework tcp congctl selection code so that the congctl entries can be const.
Don't access tcp_congctl stuff outside of tcp_congctl.c, use routines to
update t_congctl. This code is slightly now more complicated.

branches: 1.13.8; 1.13.24; 1.13.28;
Replace a simple lock with a mutex and make it static.

branches: 1.12.2; 1.12.6; 1.12.12;
__unused removal on arguments; approved by core.

branches: 1.11.2;
constify.

tcp_reno_newack: remove an __unused because it's now used.

tcp_reno_newack: regardless of sysctl setting, use L=1*SMSS when
we are doing retransmission.

implement RFC3465 appropriate byte counting.
from Kentaro A. Kurahone, with minor adjustments by me.
the ack prediction part of the original patch was omitted because
it's a separate change. reviewed by Rui Paulo.

Move comments to proper places.

Add a new tcp_congctl(9) structure member for congestion experienced callback.
Needed by HSTCP.

- sprinkle __unused on function decls.
- fix a couple of unused bugs
- no more -Wno-unused for i386

tcp_reno_newack(): bring the exact original code.
tcp_newreno_newack(): call tcp_reno_newack() if partialacks < 0.

tcp_reno_newack/tcp_newreno_newack: remove stale comments.

tcp_newreno_newack: actually inflate cwnd as it used to do.

Modular (I tried ;-) TCP congestion control API. Whenever certain conditions
happen in the TCP stack, this interface calls the specified callback to
handle the situation according to the currently selected congestion
control algorithm.
A new sysctl node was created: net.inet.tcp.congctl.{available,selected}
with obvious meanings.
The old net.inet.tcp.newreno MIB was removed.
The API is discussed in tcp_congctl(9).

In the near future, it will be possible to selected a congestion control
algorithm on a per-socket basis.

Discussed on tech-net and reviewed by <yamt>.

Rename min/max -> uimin/uimax for better honesty.

These functions are defined on unsigned int. The generic name
min/max should not silently truncate to 32 bits on 64-bit systems.
This is purely a name change -- no functional change intended.

HOWEVER! Some subsystems have

#define min(a, b) ((a) < (b) ? (a) : (b))
#define max(a, b) ((a) > (b) ? (a) : (b))

even though our standard name for that is MIN/MAX. Although these
may invite multiple evaluation bugs, these do _not_ cause integer
truncation.

To avoid `fixing' these cases, I first changed the name in libkern,
and then compile-tested every file where min/max occurred in order to
confirm that it failed -- and thus confirm that nothing shadowed
min/max -- before changing it.

I have left a handful of bootloaders that are too annoying to
compile-test, and some dead code:

cobalt ews4800mips hp300 hppa ia64 luna68k vax
acorn32/if_ie.c (not included in any kernels)
macppc/if_gm.c (superseded by gem(4))

It should be easy to fix the fallout once identified -- this way of
doing things fails safe, and the goal here, after all, is to _avoid_
silent integer truncations, not introduce them.

Maybe one day we can reintroduce min/max as type-generic things that
never silently truncate. But we should avoid doing that for a while,
so that existing code has a chance to be detected by the compiler for
conversion to uimin/uimax without changing the semantics until we can
properly audit it all. (Who knows, maybe in some cases integer
truncation is actually intended!)

Remove now unused tcpip.h includes. Some were already unused before.

Remove #ifdef INET. Same as tcp_input.c. Makes the code easier to
understand.

Also make tcp6_mtudisc() static in tcp_subr.c.

branches: 1.23.14;
Restore behaviour to pre- tcp_congctl.c:1.18 for SACK. Further analysis
of the change is required.

OK kefren@

PR/51753 tcp SACK causes SSH disconnect

Remove unnecessary inclusions of nd6.h

branches: 1.21.2;
Sweep unnecessary route.h inclusions

sprinkle _KERNEL_OPT

branches: 1.19.4; 1.19.6; 1.19.8; 1.19.10;
Cubic changes:
* correct W(t) calculation
* check wmax limits
* change W_max in slow and fast retransmit
* correct rtt approximation
Reno:
* move comment I forgot behind after fast_retransmit() split

* implement TCP CUBIC congestion control algorithm
* move tcp_sack_newack bits inside reno and newreno_fast_retransmit_newack
* notify ECN peer about cwnd shrink in [new]reno_slow_retransmit

Based on the patch proposed on tech-net@ on Nov 7 with minor improvments:
* adapt wmax for no-fast convergence case
* correct cbrt calculation for big window sizes (>750KB)

Mark a diagnostic-only variable

branches: 1.16.4; 1.16.14; 1.16.18;
simplify code a little. no functional changes.

branches: 1.15.22; 1.15.28;
Remove clause 3 and 4 from TNF licenses

branches: 1.14.2; 1.14.4;
Rework tcp congctl selection code so that the congctl entries can be const.
Don't access tcp_congctl stuff outside of tcp_congctl.c, use routines to
update t_congctl. This code is slightly now more complicated.

branches: 1.13.8; 1.13.24; 1.13.28;
Replace a simple lock with a mutex and make it static.

branches: 1.12.2; 1.12.6; 1.12.12;
__unused removal on arguments; approved by core.

branches: 1.11.2;
constify.

tcp_reno_newack: remove an __unused because it's now used.

tcp_reno_newack: regardless of sysctl setting, use L=1*SMSS when
we are doing retransmission.

implement RFC3465 appropriate byte counting.
from Kentaro A. Kurahone, with minor adjustments by me.
the ack prediction part of the original patch was omitted because
it's a separate change. reviewed by Rui Paulo.

Move comments to proper places.

Add a new tcp_congctl(9) structure member for congestion experienced callback.
Needed by HSTCP.

- sprinkle __unused on function decls.
- fix a couple of unused bugs
- no more -Wno-unused for i386

tcp_reno_newack(): bring the exact original code.
tcp_newreno_newack(): call tcp_reno_newack() if partialacks < 0.

tcp_reno_newack/tcp_newreno_newack: remove stale comments.

tcp_newreno_newack: actually inflate cwnd as it used to do.

Modular (I tried ;-) TCP congestion control API. Whenever certain conditions
happen in the TCP stack, this interface calls the specified callback to
handle the situation according to the currently selected congestion
control algorithm.
A new sysctl node was created: net.inet.tcp.congctl.{available,selected}
with obvious meanings.
The old net.inet.tcp.newreno MIB was removed.
The API is discussed in tcp_congctl(9).

In the near future, it will be possible to selected a congestion control
algorithm on a per-socket basis.

Discussed on tech-net and reviewed by <yamt>.

Restore behaviour to pre- tcp_congctl.c:1.18 for SACK. Further analysis
of the change is required.

OK kefren@

PR/51753 tcp SACK causes SSH disconnect

Remove unnecessary inclusions of nd6.h

branches: 1.21.2;
Sweep unnecessary route.h inclusions

sprinkle _KERNEL_OPT

branches: 1.19.4; 1.19.6; 1.19.8;
Cubic changes:
* correct W(t) calculation
* check wmax limits
* change W_max in slow and fast retransmit
* correct rtt approximation
Reno:
* move comment I forgot behind after fast_retransmit() split

* implement TCP CUBIC congestion control algorithm
* move tcp_sack_newack bits inside reno and newreno_fast_retransmit_newack
* notify ECN peer about cwnd shrink in [new]reno_slow_retransmit

Based on the patch proposed on tech-net@ on Nov 7 with minor improvments:
* adapt wmax for no-fast convergence case
* correct cbrt calculation for big window sizes (>750KB)

Mark a diagnostic-only variable

branches: 1.16.4; 1.16.14; 1.16.18;
simplify code a little. no functional changes.

branches: 1.15.22; 1.15.28;
Remove clause 3 and 4 from TNF licenses

branches: 1.14.2; 1.14.4;
Rework tcp congctl selection code so that the congctl entries can be const.
Don't access tcp_congctl stuff outside of tcp_congctl.c, use routines to
update t_congctl. This code is slightly now more complicated.

branches: 1.13.8; 1.13.24; 1.13.28;
Replace a simple lock with a mutex and make it static.

branches: 1.12.2; 1.12.6; 1.12.12;
__unused removal on arguments; approved by core.

branches: 1.11.2;
constify.

tcp_reno_newack: remove an __unused because it's now used.

tcp_reno_newack: regardless of sysctl setting, use L=1*SMSS when
we are doing retransmission.

implement RFC3465 appropriate byte counting.
from Kentaro A. Kurahone, with minor adjustments by me.
the ack prediction part of the original patch was omitted because
it's a separate change. reviewed by Rui Paulo.

Move comments to proper places.

Add a new tcp_congctl(9) structure member for congestion experienced callback.
Needed by HSTCP.

- sprinkle __unused on function decls.
- fix a couple of unused bugs
- no more -Wno-unused for i386

tcp_reno_newack(): bring the exact original code.
tcp_newreno_newack(): call tcp_reno_newack() if partialacks < 0.

tcp_reno_newack/tcp_newreno_newack: remove stale comments.

tcp_newreno_newack: actually inflate cwnd as it used to do.

Modular (I tried ;-) TCP congestion control API. Whenever certain conditions
happen in the TCP stack, this interface calls the specified callback to
handle the situation according to the currently selected congestion
control algorithm.
A new sysctl node was created: net.inet.tcp.congctl.{available,selected}
with obvious meanings.
The old net.inet.tcp.newreno MIB was removed.
The API is discussed in tcp_congctl(9).

In the near future, it will be possible to selected a congestion control
algorithm on a per-socket basis.

Discussed on tech-net and reviewed by <yamt>.

Remove unnecessary inclusions of nd6.h

Sweep unnecessary route.h inclusions

sprinkle _KERNEL_OPT

branches: 1.19.6;
Cubic changes:
* correct W(t) calculation
* check wmax limits
* change W_max in slow and fast retransmit
* correct rtt approximation
Reno:
* move comment I forgot behind after fast_retransmit() split

* implement TCP CUBIC congestion control algorithm
* move tcp_sack_newack bits inside reno and newreno_fast_retransmit_newack
* notify ECN peer about cwnd shrink in [new]reno_slow_retransmit

Based on the patch proposed on tech-net@ on Nov 7 with minor improvments:
* adapt wmax for no-fast convergence case
* correct cbrt calculation for big window sizes (>750KB)

Mark a diagnostic-only variable

branches: 1.16.4; 1.16.14; 1.16.18;
simplify code a little. no functional changes.

branches: 1.15.22; 1.15.28;
Remove clause 3 and 4 from TNF licenses

branches: 1.14.2; 1.14.4;
Rework tcp congctl selection code so that the congctl entries can be const.
Don't access tcp_congctl stuff outside of tcp_congctl.c, use routines to
update t_congctl. This code is slightly now more complicated.

branches: 1.13.8; 1.13.24; 1.13.28;
Replace a simple lock with a mutex and make it static.

branches: 1.12.2; 1.12.6; 1.12.12;
__unused removal on arguments; approved by core.

branches: 1.11.2;
constify.

tcp_reno_newack: remove an __unused because it's now used.

tcp_reno_newack: regardless of sysctl setting, use L=1*SMSS when
we are doing retransmission.

implement RFC3465 appropriate byte counting.
from Kentaro A. Kurahone, with minor adjustments by me.
the ack prediction part of the original patch was omitted because
it's a separate change. reviewed by Rui Paulo.

Move comments to proper places.

Add a new tcp_congctl(9) structure member for congestion experienced callback.
Needed by HSTCP.

- sprinkle __unused on function decls.
- fix a couple of unused bugs
- no more -Wno-unused for i386

tcp_reno_newack(): bring the exact original code.
tcp_newreno_newack(): call tcp_reno_newack() if partialacks < 0.

tcp_reno_newack/tcp_newreno_newack: remove stale comments.

tcp_newreno_newack: actually inflate cwnd as it used to do.

Modular (I tried ;-) TCP congestion control API. Whenever certain conditions
happen in the TCP stack, this interface calls the specified callback to
handle the situation according to the currently selected congestion
control algorithm.
A new sysctl node was created: net.inet.tcp.congctl.{available,selected}
with obvious meanings.
The old net.inet.tcp.newreno MIB was removed.
The API is discussed in tcp_congctl(9).

In the near future, it will be possible to selected a congestion control
algorithm on a per-socket basis.

Discussed on tech-net and reviewed by <yamt>.