oggdec: Pass packets to header() until the stream is done with them

This fixes some old ogm files that had the 3rd vorbis header after a data
packet in another stream. This is invalid in ogg, but this change shouldn't
affect the behaviour of any valid file.

Originally committed as revision 22478 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/oggdec.h

@@ -62,7 +62,6 @@ struct ogg_stream {
     unsigned int pflags;
     unsigned int pduration;
     uint32_t serial;
-    uint32_t seq;
     uint64_t granule;
     int64_t lastpts;
     int64_t lastdts;