stagefright: Fix 24-bit WAV

 * When 24-bit output is enabled, we need to ensure that padding
   to 32 bits is done correctly.
 * Create new output buffers which conform to the correct format.

Change-Id: I5c07027ee8d3040147698c1f484b40991f943c03
cameraservice: Resolve message vs start/stop preview races

Move the mutex in start/stopPreview to include the metadata message
management. Fast start/stop sequences could (and would) eventually
cause the messages to be enabled/disabled out of sequence (or while
the camera wasn't ready for it)

Fixes BACON-173

Change-Id: I367bc45729ce2e858fea972f35e881a755c6021a
Merge branch 'cm-11.0' of https://github.com/CyanogenMod/android_frameworks_av into cm-11.0