add vspx fourcc to mpeg4 in riff.c

Originally committed as revision 21269 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/riff.c

@@ -77,6 +77,7 @@ const AVCodecTag ff_codec_bmp_tags[] = {
     { CODEC_ID_MPEG4,        MKTAG('E', 'M', '4', 'A') },
     { CODEC_ID_MPEG4,        MKTAG('M', '4', 'C', 'C') }, /* Divio MPEG-4 */
     { CODEC_ID_MPEG4,        MKTAG('S', 'N', '4', '0') },
+    { CODEC_ID_MPEG4,        MKTAG('V', 'S', 'P', 'X') },
     { CODEC_ID_MSMPEG4V3,    MKTAG('D', 'I', 'V', '3') }, /* default signature when using MSMPEG4 */
     { CODEC_ID_MSMPEG4V3,    MKTAG('M', 'P', '4', '3') },
     { CODEC_ID_MSMPEG4V3,    MKTAG('M', 'P', 'G', '3') },