DO NOT MERGE: Sensor multi HAL

DO NOT MERGE: Sensor multi HAL

Squashed commit of:

Move sensors multi HAL to libhardware

Added a SensorEventQueue, a circular buffer meant for reading with one thread
and polling a subhal with another. The writing thread gets access to pointers
in the internal buffer. This design avoids a memcpy on write when the multihal
fetches subhal events using poll().

Unit-tests include multithreaded reading and writing lots of events, in
random-sized chunks.

This is not used by the multihal yet. That will be a different CL.

MultiHal multithreaded polling

Tests SensorEventQueue I/O when the queue is full.
Reduced debug logging in multihal.

deactivated multihal logspam, made warnings warnings, left critical startup info

Removed unneeded linux/input.h includes, to fix Mac SDK build

Change-Id: I1e35508949df98a1acef7a4a2d012eea87b4a5eb