vorbis: also check comments for comment metadata

The comments field is also encoded as "COMMENTS=" instead of description. For example, Audacity encodes the comment box as "COMMENTS=" instead of "DESCRIPTION=".
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

modules/demux/vorbis.h

@@ -155,6 +155,10 @@ static inline void vorbis_ParseComment( vlc_meta_t **pp_meta, const uint8_t *p_d
         else IF_EXTRACT("COPYRIGHT=", Copyright )
         else IF_EXTRACT("ORGANIZATION=", Publisher )
         else IF_EXTRACT("DESCRIPTION=", Description )
+        else if( !hasDescription )
+        {
+            IF_EXTRACT("COMMENTS=", Description )
+        }
         else IF_EXTRACT("GENRE=", Genre )
         else IF_EXTRACT("DATE=", Date )
         else if( !strncasecmp( psz, "METADATA_BLOCK_PICTURE=", strlen("METADATA_BLOCK_PICTURE=")))