Minimize memory leak risks.

Remove implicit back-reference from playback thread to player.
Use new MediaCodecList APIs on L.
Add support for extracting Vorbis audio in WebM Extractor.
Add missing class.
Add receiver for HDMI plugged-in configuration changes.
Factor out AudioTrack from MediaCodecAudioTrackRenderer.

AudioTrack contains the portions of MediaCodecAudioTrackRenderer that handle the
platform AudioTrack instance, including synchronization (playback position
smoothing), non-blocking writes and releasing.

This refactoring should not affect the behavior of audio playback, and is in
preparation for adding an Ac3PassthroughAudioTrackRenderer that will use the
AudioTrack.
MediaCodecTrackRenderer: Avoid excessive garbage generation

Looking up a long in a HashSet<Long> auto boxes the long and leaves
it for the GC. As decodeOnly is relatively infrequent it's much
better to do a simple linear search in a List<Long>. That way
we can avoid boxing every incoming time stamp value. In the general
case this will be linear searching in an empty list, a very fast
operation.

Signed-off-by: Jonas Larsson <jonas@hallerud.se>
Bring internal/external branches closer.

- Unredact internal error ids.
- Move images.
Merge pull request #147 from jonasl/dev-gc

MediaCodecTrackRenderer: Avoid excessive garbage generation