This updates mod_cron to have much more unix-cron like behavior. The old
version would start an interval timer whenever ejabberd started, which isn't
a particularly useful starting point (I don't care for my regular activities
to be based on when the server was last booted).
This version allows two types of entries: timers based on an interval,
e.g. every 10 seconds (which would start on the minute, so occur at
00:00s, 00:10s, 00:20s etc) and fixed timers occuring once per
parent-interval. e.g. a fixed 10s timer would occur at 00:10s,
01:10s etc. (ie its a one minute interval happening 10seconds
after every minute).
aecd0e7deb