Add support for timeconting in userland.

This diff exposes parts of clock_gettime(2) and gettimeofday(2) to
userland via libc eliberating processes from the need for a context
switch everytime they want to count the passage of time.

If a timecounter clock can be exposed to userland than it needs to set
its tc_user member to a non-zero value. Tested with one or multiple
counters per architecture.

The timing data is shared through a pointer found in the new ELF
auxiliary vector AUX_openbsd_timekeep containing timehands information
that is frequently updated by the kernel.

Timing differences between the last kernel update and the current time
are adjusted in userland by the tc_get_timecount() function inside the
MD usertc.c file.

This permits a much more responsive environment, quite visible in
browsers, office programs and gaming (apparently one is are able to fly
in Minecraft now).

Tested by robert@, sthen@, naddy@, kmos@, phessler@, and many others!

OK from at least kettenis@, cheloha@, naddy@, sthen@

Don't add setjmp.S twice.

alloca.c cannot be used

Revert (leaving the complex math part alone). Some stuff is depending
on this historical behavior; so we're stuck in this stupid situation.
No cookie for me.

Move fabs(3), frexp(3), and modf(3) to libm--nothing has been using
them in libc for a very long time. OK guenther@.

remove from gen so that lint doesn't check gen if assembly versions
are available. spotted by theo

- ldexp implementation has issues. switch to the one from libm
- remove frexp in hppa64, cloned from hppa
- move generic ieee754 implementations of modf and ldexp to gen
ok kettenis@, "looks good" millert@

- move isinf, isnan dups to gen, since most is ieee 754
- is{inf,nan} should be macros for real-floating, so rename to
__is{inf,nan}, per C99
- implement C99 __fpclassify(), __fpclassifyf(), __isfinite(),
__isfinitef(), __isnormal(), __isnormalf(), __signbit(), __signbitf()
- long functions added, but not yet enabled, till ieee.h is fixed
- implement vax equivalents of the functions
- reimplement isinff, isnanf in a better way, and move to libc
- add qnan bytes for all archs
- bump major
man pages will follow
ok millert@. arm bits looked over by drahn@
discussed w/ theo, who showed the right direction, to put these
functions in libc

if we pull in a .S file, we must fake out the lint with a .c file
for this first cut, we will do this for alloca() using alloca.c by
adding it to LSRCS

Replace broken frexp() with a working one from FreeBSD. There's
no need to have a copy for each platform with ieee floating point,
only vax needs a special version (which probably has similar bugs).
OK and with help from otto@

Add Doug Gwyn's portable alloca() for platforms w/o an assembler
version. Normally, gcc provides its own alloca() (unless -fno-builtin
is specified). The C version is decidedly suboptimal--we really
need proper assembler versions but this will work as a stop-gap
measure.

kill unused line

More fp-related libc pieces for hppa.
This enables awk to link.

implement the setjmp/longjmp family, based on fredette@'s work

some basic framework

some missing parts; sys is not ready yet

Don't add setjmp.S twice.

alloca.c cannot be used

Revert (leaving the complex math part alone). Some stuff is depending
on this historical behavior; so we're stuck in this stupid situation.
No cookie for me.

Move fabs(3), frexp(3), and modf(3) to libm--nothing has been using
them in libc for a very long time. OK guenther@.

remove from gen so that lint doesn't check gen if assembly versions
are available. spotted by theo

- ldexp implementation has issues. switch to the one from libm
- remove frexp in hppa64, cloned from hppa
- move generic ieee754 implementations of modf and ldexp to gen
ok kettenis@, "looks good" millert@

- move isinf, isnan dups to gen, since most is ieee 754
- is{inf,nan} should be macros for real-floating, so rename to
__is{inf,nan}, per C99
- implement C99 __fpclassify(), __fpclassifyf(), __isfinite(),
__isfinitef(), __isnormal(), __isnormalf(), __signbit(), __signbitf()
- long functions added, but not yet enabled, till ieee.h is fixed
- implement vax equivalents of the functions
- reimplement isinff, isnanf in a better way, and move to libc
- add qnan bytes for all archs
- bump major
man pages will follow
ok millert@. arm bits looked over by drahn@
discussed w/ theo, who showed the right direction, to put these
functions in libc

if we pull in a .S file, we must fake out the lint with a .c file
for this first cut, we will do this for alloca() using alloca.c by
adding it to LSRCS

Replace broken frexp() with a working one from FreeBSD. There's
no need to have a copy for each platform with ieee floating point,
only vax needs a special version (which probably has similar bugs).
OK and with help from otto@

Add Doug Gwyn's portable alloca() for platforms w/o an assembler
version. Normally, gcc provides its own alloca() (unless -fno-builtin
is specified). The C version is decidedly suboptimal--we really
need proper assembler versions but this will work as a stop-gap
measure.

kill unused line

More fp-related libc pieces for hppa.
This enables awk to link.

implement the setjmp/longjmp family, based on fredette@'s work

some basic framework

some missing parts; sys is not ready yet