time: change gettime return values & add gettime_unix
time: change gettime return values & add gettime_unix

Change the type of a clock that gettime returns to a monotonic timestamp
from an arbitrary point in the past.  Also, introduce gettime_unix which
returns the values gettime used to.

Signed-off-by: Josef 'Jeff' Sipek <a620f141433c70aa9e43778305a6c68cbfadfb25@josefsipek.net>

jeffpc/libjeffpc,jeffpc/libjeffpc,jeffpc/libjeffpc,jeffpc/libjeffpc