Parse the OpaqueData field for every AVStream represented by this "set of

Parse the OpaqueData field for every AVStream represented by this "set of
streams" (a single RTSPStream / RDTDemuxContext can represent several
AVStreams, that's just how Real/RDT was designed...). This will fill in
most of the AVStream/AVCodecContext header fields, similar to reading a
RM file header would. See "[PATCH] multi-stream MDPR parsing" thread on
mailinglist.

Originally committed as revision 16468 to svn://svn.ffmpeg.org/ffmpeg/trunk