timer-time: A new module to check for timer_settime()

timer-time: A new module to check for timer_settime()

* m4/timer_time.m4: Check for the POSIX function.
* modules/timer-time: Add the new module.
* MODULES.html.sh (Compat checks for POSIX:2008 functions):
Mention it.
* doc/posix-functions/timer_create.texi: Add timer-time as
the module, and update the platforms where unavailable.
* doc/posix-functions/timer_delete.texi: Likewise.
* doc/posix-functions/timer_gettime.texi: Likewise.
* doc/posix-functions/timer_settime.texi: Likewise.

Signed-off-by: Pádraig Brady <P@draigBrady.com>