Add formats for UHJ with muLaw, and ADPCM for 2-channel UHJ
ADPCM doesn't seem to be well defined for more than two channels, even though
there doesn't seem to be any issue with simply increasing the channel step over
interleaved data (ffmpeg refuses to create IMA4 or MSADPCM files with more than
two channels, and its decoder behaves oddly different when channels > 2). So
IMA4 and MSADPCM can only safely handle 2-channel UHJ.
There's no problem with muLaw supporting 2-, 3-, or 4-channel UHJ though.