[Cin] truehd patches from ffmpeg git

so.. patches mostly applicable to ffmpeg-4.4 while I slightly edited 'last frame' fix due to other ffmpeg changes apply 'last frame' and '24-bit' for encoding truehd hopefully lossless apply two mlpdec patches for more correct decoder flush/crc check try to apply mlp.h and libavformat patches for timestamps in demuxer... stop-returning-empty for mlpenc not tested. after all this patching both ffmpeg and cin should work better with truehd streams (still require 'strict -2' in profile) there were other fixes and code movements but i hope those patches can fix real bugs and allow losless re-encoding between pcm and truehd (check crc's!)