Const correctness for vorbis_comment

Originally committed as revision 22474 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/oggdec.h

@@ -115,7 +115,7 @@ extern const struct ogg_codec ff_vorbis_codec;
 
 extern const AVMetadataConv ff_vorbiscomment_metadata_conv[];
 
-int ff_vorbis_comment(AVFormatContext *ms, AVMetadata **m, uint8_t *buf, int size);
+int ff_vorbis_comment(AVFormatContext *ms, AVMetadata **m, const uint8_t *buf, int size);
 
 static inline int
 ogg_find_stream (struct ogg * ogg, int serial)

libavformat/oggparsevorbis.c

@@ -42,7 +42,7 @@ const AVMetadataConv ff_vorbiscomment_metadata_conv[] = {
 };
 
 int
-ff_vorbis_comment(AVFormatContext * as, AVMetadata **m, uint8_t *buf, int size)
+ff_vorbis_comment(AVFormatContext * as, AVMetadata **m, const uint8_t *buf, int size)
 {
     const uint8_t *p = buf;
     const uint8_t *end = buf + size;