* DV demuxer is now capable of decoding auxilary audio stream. So,

      everybody who still uses second streo track for dubbing can
     now export it.

   * void* -> DVDemuxContext* change (per Fabrice's suggestion).

   * -dv1394 capture now works in all modes.

Originally committed as revision 2458 to svn://svn.ffmpeg.org/ffmpeg/trunk