lavc: support ZenoXVID custom tag

Looks like this kind of samples are produced by certain Russian
equipment.

libavcodec/h263dec.c

@@ -441,7 +441,7 @@ retry:
     if(s->xvid_build==-1 && s->divx_version==-1 && s->lavc_build==-1){
         if(s->stream_codec_tag == AV_RL32("XVID") ||
            s->codec_tag == AV_RL32("XVID") || s->codec_tag == AV_RL32("XVIX") ||
-           s->codec_tag == AV_RL32("RMP4") ||
+           s->codec_tag == AV_RL32("RMP4") || s->codec_tag == AV_RL32("ZMP4") ||
            s->codec_tag == AV_RL32("SIPP")
            )
             s->xvid_build= 0;

libavformat/riff.c

@@ -55,6 +55,7 @@ const AVCodecTag ff_codec_bmp_tags[] = {
     { AV_CODEC_ID_MPEG4,        MKTAG('M', 'P', '4', 'S') },
     { AV_CODEC_ID_MPEG4,        MKTAG('M', '4', 'S', '2') },
     { AV_CODEC_ID_MPEG4,        MKTAG( 4 ,  0 ,  0 ,  0 ) }, /* some broken avi use this */
+    { AV_CODEC_ID_MPEG4,        MKTAG('Z', 'M', 'P', '4') }, /* some broken avi use this */
     { AV_CODEC_ID_MPEG4,        MKTAG('D', 'I', 'V', '1') },
     { AV_CODEC_ID_MPEG4,        MKTAG('B', 'L', 'Z', '0') },
     { AV_CODEC_ID_MPEG4,        MKTAG('m', 'p', '4', 'v') },