Miscellaneous loop test improvements

Enable HEADATEND event to see whether looping causes that event.
Recover from prefetch errors using the new approach of condition signal rather than polling.
Check result returned by GetFillLevel.

Other changes:
 - Make assert work.
 - Pass NULL as 3rd parameter to RegisterCallback when context is not needed.
 - Use CheckErr instead of assert when checking result codes.
 - Add comments.

Change-Id: I972b9eca9836e62141b6a078345f091e60689321
2 files changed
tree: 1ecad19fa0dda526fbfebeaf41dca8c58a3cd5a6
  1. audio_effects/
  2. mca/
  3. wilhelm/
  4. CleanSpec.mk