It is supported only by a few decoders (h263, h263p, mpeg(1|2|)video
and mpeg4) and is entirely redundant with parsers. Furthermore, using
it leads to missing frames, as flushing the decoder at the end does not
work properly.

Co-authored-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>