mpd.conf(5): Document the existence of musicbrainz_ tags

doc/mpd.conf.5

@@ -252,11 +252,12 @@ when saving playlists.  The default is "no".
 This specifies the tag types that will be scanned for and made available to
 clients.  Note that you must recreate (not update) your database for changes to
 this parameter to take effect.  Possible values are artist, album, title,
-track, name, genre, date, composer, performer, comment, and disc.  Multiple
-tags may be specified as a comma separated list.  An example value is
-"artist,album,title,track".  The special value "none" may be used alone to
-disable all metadata.  The default is to use all known tag types except for
-comments.
+track, name, genre, date, composer, performer, comment, disc,
+musicbrainz_artistid, musicbrainz_albumid, musicbrainz_albumartistid,
+musicbrainz_trackid.  Multiple tags may be specified as a comma separated list.
+An example value is "artist,album,title,track".  The special value "none" may
+be used alone to disable all metadata.  The default is to use all known tag
+types except for comments and those starting with "musicbrainz".
 .TP
 .B auto_update <yes or no>
 This specifies the wheter to support automatic update of music database when

doc/mpdconf.example

@@ -113,10 +113,9 @@
 #
 #save_absolute_paths_in_playlists	"no"
 #
-# This setting defines a list of tag types that will be extracted during the 
-# audio file discovery process. Optionally, 'comment' can be added to this
-# list.
-#
+# This setting defines a list of tag types that will be extracted during the
+# audio file discovery process. The complete list of possible values can be
+# found in the mpd.conf man page.
 #metadata_to_use	"artist,album,title,track,name,genre,date,composer,performer,disc"
 #
 # This setting enables automatic update of MPD's database when files in