mp3adu: Set the channel layout properly

This fixes decoding, broken since 7e35037.

This is similar to what was done for the normal mp3 decoder in
f4a86bc9.

Signed-off-by: Martin Storsjö <martin@martin.st>
parseutils: fix discarding const attribute warning
rtsp: suppress a incompatible pointer types warning
img2: add stereo 3d still picture file extensions
changelog: drop redundant new attribute
mpegts: add HEVC registration descriptor