libavformat: Add an ff_ prefix to some lavf internal symbols

Prefix the functions/tables brktimegm, pcm_read_seek,
dv_offset_reset, voc_get_packet, codec_movaudio_tags,
codec_movvideo_tags.

After this, lavf has no global symbols without the proper prefix.

Signed-off-by: Martin Storsjö <martin@martin.st>

libavformat/soxdec.c

@@ -148,5 +148,5 @@ AVInputFormat ff_sox_demuxer = {
     .read_probe     = sox_probe,
     .read_header    = sox_read_header,
     .read_packet    = sox_read_packet,
-    .read_seek      = pcm_read_seek,
+    .read_seek      = ff_pcm_read_seek,
 };