avformat: add dvbsub demuxer

This is needed for probing some dvbsub streams in mpegts

Fixes part of ticket4221

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/allformats.c

@@ -113,6 +113,7 @@ void av_register_all(void)
     REGISTER_MUXDEMUX(DTS,              dts);
     REGISTER_DEMUXER (DTSHD,            dtshd);
     REGISTER_MUXDEMUX(DV,               dv);
+    REGISTER_DEMUXER (DVBSUB,           dvbsub);
     REGISTER_DEMUXER (DXA,              dxa);
     REGISTER_DEMUXER (EA,               ea);
     REGISTER_DEMUXER (EA_CDATA,         ea_cdata);