demuxer ffmpeg: move m_streams into a map, drop MAX_STREAMS
dvdplayer: move extradata cleanup to CDVDDemuxStream destructor
dvdplayer: keep temporary stream pointer in ffmpeg AddStream
dvdplayer: keep ffmpeg demuxer indexes in continous order
demuxer ffmpeg: handle pmt changes
Merge pull request #1757 from FernetMenta/streams

make ffmpeg demuxer observe pmt changes