Bug fixes include:
- keep interrupts disabled during lpm_sleep() so that we don't
miss any interrupts we may have been expecting
- check that the pending etimer isn't already expired (and don't sleep
at all if it is)
- check that the about-to-be scheduled rtimer wakeup is neither too
far into the future nor too close into the future (or even in the
past) before actually setting the interrupt (should fix#1509); If
the time is out of bounds we use a default min or max value instead.
- Correctly handle LPM_MODE_MAX_SUPPORTED set to zero (and added a
macro for the zero value) so that sleeping can be disabled altogether
- If no etimer is set, we specify a wakeup time which is reasonably far
into the future instead of setting none at all (this will save on
power consumption whenever no etimers are set).
Also did a bit of refactoring in that some long functions were broken
into multiple functions.
786aa19cbd