Bug 870480 - Notify wake lock listeners when a process adds or removes a wake lock, even if the wake lock itself doesn't change state. r=kanru

This also fixes two other bugs:

1) If a process crashed while holding a wake lock, we'd send a wake lock changed notification without including the list of locking processes.  This could cause us to incorrectly believe that no processes were holding the lock.

2) If a process crashed while holding a wake lock on topic X, and if no other process held a wake lock on that topic, and there were no wake lock listeners registered, we wouldn't remove X from our hashtable of wake lock topics.  We would correctly record the fact that the lock was not held, so this bug was benign.