Treat SIPP like xvid, fixed issue1966

Originally committed as revision 23336 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/h263dec.c

@@ -428,7 +428,9 @@ 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("SIPP")
+           )
             s->xvid_build= 0;
 #if 0
         if(s->codec_tag == AV_RL32("DIVX") && s->vo_type==0 && s->vol_control_parameters==1