Demux all parts of concatenated H.264.

We may or may not be able to play the latter parts
but not demuxing at all seems like the worst possible behaviour.
Fixes playback of e.g.
http://playlist.yahoo.com/makeplaylist.dll?sid=128114687&sdm=web&pt=rd


As a proper solution either multiple video streams should
be exported or side data should be used to update extradata
if necessary.

Signed-off-by: Reimar Döffinger <Reimar.Doeffinger@gmx.de>