Prevent some alarm pathologies

* Sanity-check the recurrence interval.  Some buggy apps pass seconds
  where the API expects milliseconds, with the result that the device
  pins the CPU at 100% trying to deliver alarm broadcasts every 60 ms
  or what have you.  The minimum recurrence is now 1 minute.

* Sanity-check alarms being scheduled for the immediate future.  As
  with the above this will catch people trying to schedule alarms
  in a spammy way that keeps the device from entering low-power state.
  The minimum futurity of a new alarm is now 5 seconds.

Bug 17495168

Change-Id: If8ff7d88da48960532ac21a0ba20094af9912603