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@

When system calls indicate an error they return -1, not some arbitrary
value < 0. errno is only updated in this case. Change all (most?)
callers of syscalls to follow this better, and let's see if this strictness
helps us in the future.

Return monotonically increasing values.

The latest POSIX description of times(3) (and all others I can find)
suggests that times(3) should return monotonically increasing values
and that these values are only useful for real time interval measurement.
All extant uses of times(3) confirm that this expectation is shared by
application programmers.

So, change gettimeofday(2) to clock_gettime(2)/CLOCK_MONOTONIC to ensure
the return value increases monotonically, even if the system clock is
changed by the superuser. Then update the manpage accordingly.

While we're updating the manpage, move the information about the return
values to a new RETURN VALUES section to bring times.3 up to speed with
other library man pages.

Manpage changes kicked around on tech@ with millert@ and jmc@.

times.3 ok millert@ tb@ jmc@
times.c ok millert@ tb@

(struct timezone *)0 -> NULL

Move to the <limits.h> universe.
review by millert, binary checking process with doug, concept with guenther

zap remaining rcsid.

Kill old files that are no longer compiled.

okay theo

ansify function definitions and zap some `register'

ok millert@

Remove the advertising clause in the UCB license which Berkeley
rescinded 22 July 1999. Proofed by myself and Theo.

Fix RCS ids
Make sure everything uses {SYS,}LIBC_SCCS properly

branches: 1.1.1;
Initial revision

When system calls indicate an error they return -1, not some arbitrary
value < 0. errno is only updated in this case. Change all (most?)
callers of syscalls to follow this better, and let's see if this strictness
helps us in the future.

Return monotonically increasing values.

The latest POSIX description of times(3) (and all others I can find)
suggests that times(3) should return monotonically increasing values
and that these values are only useful for real time interval measurement.
All extant uses of times(3) confirm that this expectation is shared by
application programmers.

So, change gettimeofday(2) to clock_gettime(2)/CLOCK_MONOTONIC to ensure
the return value increases monotonically, even if the system clock is
changed by the superuser. Then update the manpage accordingly.

While we're updating the manpage, move the information about the return
values to a new RETURN VALUES section to bring times.3 up to speed with
other library man pages.

Manpage changes kicked around on tech@ with millert@ and jmc@.

times.3 ok millert@ tb@ jmc@
times.c ok millert@ tb@

(struct timezone *)0 -> NULL

Move to the <limits.h> universe.
review by millert, binary checking process with doug, concept with guenther

zap remaining rcsid.

Kill old files that are no longer compiled.

okay theo

ansify function definitions and zap some `register'

ok millert@

Remove the advertising clause in the UCB license which Berkeley
rescinded 22 July 1999. Proofed by myself and Theo.

Fix RCS ids
Make sure everything uses {SYS,}LIBC_SCCS properly

branches: 1.1.1;
Initial revision

Return monotonically increasing values.

The latest POSIX description of times(3) (and all others I can find)
suggests that times(3) should return monotonically increasing values
and that these values are only useful for real time interval measurement.
All extant uses of times(3) confirm that this expectation is shared by
application programmers.

So, change gettimeofday(2) to clock_gettime(2)/CLOCK_MONOTONIC to ensure
the return value increases monotonically, even if the system clock is
changed by the superuser. Then update the manpage accordingly.

While we're updating the manpage, move the information about the return
values to a new RETURN VALUES section to bring times.3 up to speed with
other library man pages.

Manpage changes kicked around on tech@ with millert@ and jmc@.

times.3 ok millert@ tb@ jmc@
times.c ok millert@ tb@

(struct timezone *)0 -> NULL

Move to the <limits.h> universe.
review by millert, binary checking process with doug, concept with guenther

zap remaining rcsid.

Kill old files that are no longer compiled.

okay theo

ansify function definitions and zap some `register'

ok millert@

Remove the advertising clause in the UCB license which Berkeley
rescinded 22 July 1999. Proofed by myself and Theo.

Fix RCS ids
Make sure everything uses {SYS,}LIBC_SCCS properly

branches: 1.1.1;
Initial revision

(struct timezone *)0 -> NULL

Move to the <limits.h> universe.
review by millert, binary checking process with doug, concept with guenther

zap remaining rcsid.

Kill old files that are no longer compiled.

okay theo

ansify function definitions and zap some `register'

ok millert@

Remove the advertising clause in the UCB license which Berkeley
rescinded 22 July 1999. Proofed by myself and Theo.

Fix RCS ids
Make sure everything uses {SYS,}LIBC_SCCS properly

branches: 1.1.1;
Initial revision