DO NOT MERGE Use POSIX timer API for wake alarms instead of OSI callouts.

DO NOT MERGE Use POSIX timer API for wake alarms instead of OSI callouts.

This change increases RFCOMM throughput by a little over 50%. We
were paying a pretty major cost in setting up / tearing down wake
timers by going through JNI and Binder over to AlarmService.

There are a few gotchas with this implementation, particularly
because the Linux kernel implementation of wake timers is somewhat
buggy.

Bug: 23375670
Change-Id: I27558f439e57696d912b968f56a48e5e4098860b