Use AVERROR_PATCHWELCOME instead of AVERROR(ENOTSUP)

Originally committed as revision 10111 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/vocenc.c

@@ -34,7 +34,7 @@ static int voc_write_header(AVFormatContext *s)
 
     if (s->nb_streams != 1
         || s->streams[0]->codec->codec_type != CODEC_TYPE_AUDIO)
-        return AVERROR(ENOTSUP);
+        return AVERROR_PATCHWELCOME;
 
     put_buffer(pb, voc_magic, sizeof(voc_magic) - 1);
     put_le16(pb, header_size);