mlv_dump with LJ92 and 10/12-bit support
Cherry-picked from raw_video_10bit_12bit and crop_rec_4k branches. Identical to crop_rec_4k's mlv_dump (which includes 10/12-bit support), has all the history from the experimental branches, only touches mlv_dump.c and related files.
As long as it doesn't break compatibility with 14-bit files, it's probably time to include it into unified.
@bouncyball's updates should merge cleanly on top of this, too (as it's identical to crop_rec_4k).