Jason Evans 45a5bf6772 Do not advance decay epoch when time goes backwards.
Instead, move the epoch backward in time.  Additionally, add
nstime_monotonic() and use it in debug builds to assert that time only
goes backward if nstime_update() is using a non-monotonic time source.
2016-10-10 22:31:37 -07:00
..
2016-02-29 10:45:49 -08:00