Added dummy decoders for AC3, TrueHD, DTS, DTS-HD and DTS-MA

This avoids having to include actual decode logic for
all of these different audio formats in FFMPEG while
still being able to identify the streams for proper passthrough.

Change-Id: I12a5b2393a087e79f078c2d8310b5ca35fd8c859
5 files changed