ISO/IEC 13818-1:2000/Amd.2:2003 Adds support for signalling
a stream_id_extension.  This is used in mapping standards
for Dirac/VC-2 and VC-1.
Signed-off-by: David Flynn <davidf@rd.bbc.co.uk>
Signed-off-by: Laurent Aimar <fenrir@videolan.org>