all platforms, kernel: remove __HAVE_CLOCKINTR symbol

Every platform made the clockintr switch at least six months ago.
The __HAVE_CLOCKINTR symbol is now redundant. Remove it.

Prompted by claudio@.

Link: https://marc.info/?l=openbsd-tech&m=168826181015032&w=2

"makes sense" mlarkin@

arm64: switch to clockintr(9)

Switch arm64 to the clockintr(9) subsystem.

- Remove the custom per-CPU clock interrupt schedule from agtimer(4).
- Remove the custom randomized statclock() pieces from agtimer(4).
- Add agtimer_rearm(), agtimer_trigger(), and wire up agtimer_intrclock.

There is one wart:

- The AArch64 spec says that a value written to CNTV_TVAL_EL0 is
"treated as a signed 32-bit integer" [1]. kettenis@ doesn't know
what to make of this. I'm capping the value at INT32_MAX for
now. It's possible I am misreading this, though.

Tested by kettenis@ on his Apple M1 mini. Tested by me on my
Raspberry Pi 4B.

Link: https://marc.info/?l=openbsd-tech&m=166776342503304&w=2

[1] "Arm Architecture Reference Manual for A-profile architecture"
issue I.a, section D17.11.27 ("CNTV_TVAL_EL0").

ok kettenis@

#define _MAX_PAGE_SHIFT in MD _types.h as the maximum pagesize an arch
needs (looking at you sgi, but others required this before). This is for
the circumstances we need pagesize known at compile time, not getpagesize()
runtime. Use it for malloc storage sizes, for shm, and to set pthread stack
default sizes. The stack sizes were a mess, and pushing them towards
page-aligned is healthy move (which will also be needed by the coming
stack register checker)
ok guenther kettenis, discussion with stefan

Setjmp and longjmp save/restore 13 registers in a label_t struct,
not only 11 registers.

Update and add wide character support types.

Import of OpenBSD/arm64

This commit contains all the kernel files related to the OpenBSD/arm64
port. It is based on the PowerPC pmap, loongson, arm/armv7 code and
FreeBSD aarch64 code. Hard work done by Dale Rahn.

arm64: switch to clockintr(9)

Switch arm64 to the clockintr(9) subsystem.

- Remove the custom per-CPU clock interrupt schedule from agtimer(4).
- Remove the custom randomized statclock() pieces from agtimer(4).
- Add agtimer_rearm(), agtimer_trigger(), and wire up agtimer_intrclock.

There is one wart:

- The AArch64 spec says that a value written to CNTV_TVAL_EL0 is
"treated as a signed 32-bit integer" [1]. kettenis@ doesn't know
what to make of this. I'm capping the value at INT32_MAX for
now. It's possible I am misreading this, though.

Tested by kettenis@ on his Apple M1 mini. Tested by me on my
Raspberry Pi 4B.

Link: https://marc.info/?l=openbsd-tech&m=166776342503304&w=2

[1] "Arm Architecture Reference Manual for A-profile architecture"
issue I.a, section D17.11.27 ("CNTV_TVAL_EL0").

ok kettenis@

#define _MAX_PAGE_SHIFT in MD _types.h as the maximum pagesize an arch
needs (looking at you sgi, but others required this before). This is for
the circumstances we need pagesize known at compile time, not getpagesize()
runtime. Use it for malloc storage sizes, for shm, and to set pthread stack
default sizes. The stack sizes were a mess, and pushing them towards
page-aligned is healthy move (which will also be needed by the coming
stack register checker)
ok guenther kettenis, discussion with stefan

Setjmp and longjmp save/restore 13 registers in a label_t struct,
not only 11 registers.

Update and add wide character support types.

Import of OpenBSD/arm64

This commit contains all the kernel files related to the OpenBSD/arm64
port. It is based on the PowerPC pmap, loongson, arm/armv7 code and
FreeBSD aarch64 code. Hard work done by Dale Rahn.

#define _MAX_PAGE_SHIFT in MD _types.h as the maximum pagesize an arch
needs (looking at you sgi, but others required this before). This is for
the circumstances we need pagesize known at compile time, not getpagesize()
runtime. Use it for malloc storage sizes, for shm, and to set pthread stack
default sizes. The stack sizes were a mess, and pushing them towards
page-aligned is healthy move (which will also be needed by the coming
stack register checker)
ok guenther kettenis, discussion with stefan

Setjmp and longjmp save/restore 13 registers in a label_t struct,
not only 11 registers.

Update and add wide character support types.

Import of OpenBSD/arm64

This commit contains all the kernel files related to the OpenBSD/arm64
port. It is based on the PowerPC pmap, loongson, arm/armv7 code and
FreeBSD aarch64 code. Hard work done by Dale Rahn.

Setjmp and longjmp save/restore 13 registers in a label_t struct,
not only 11 registers.

Update and add wide character support types.

Import of OpenBSD/arm64

This commit contains all the kernel files related to the OpenBSD/arm64
port. It is based on the PowerPC pmap, loongson, arm/armv7 code and
FreeBSD aarch64 code. Hard work done by Dale Rahn.