Set AVFMT_NOTIMESTAMPS flag for mp3 muxer

Fixes issue 1026

Originally committed as revision 22916 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/mp3.c

@@ -360,6 +360,7 @@ AVOutputFormat mp3_muxer = {
     mp3_write_header,
     mp3_write_packet,
     mp3_write_trailer,
+    AVFMT_NOTIMESTAMPS,
     .metadata_conv = ff_id3v2_metadata_conv,
 };
 #endif