EvTimer::again

Description

This will act as if the timer timed out and restart it again if it is repeating. The exact semantics are:

1. if the timer is pending, its pending status is cleared.
2. if the timer is started but non-repeating, stop it (as if it timed out).
3. if the timer is repeating, either start it if necesssary (with the repeat value), or reset the running timer to the repeat value.