vfwcap: support MJPG compressed streams.

Patch by Nash Tsai <nash dot tsai at gmail dot com>

Originally committed as revision 22004 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavdevice/vfwcap.c

@@ -74,6 +74,9 @@ static enum CodecID vfw_codecid(DWORD biCompression)
     switch(biCompression) {
     case MKTAG('d', 'v', 's', 'd'):
         return CODEC_ID_DVVIDEO;
+    case MKTAG('M', 'J', 'P', 'G'):
+    case MKTAG('m', 'j', 'p', 'g'):
+        return CODEC_ID_MJPEG;
     }
     return CODEC_ID_NONE;
 }