playlist: deleteASongFromPlaylist takes a const Song *

src/playlist.c

@@ -775,7 +775,7 @@ enum playlist_result deleteFromPlaylistById(int id)
 	return deleteFromPlaylist(song);
 }
 
-void deleteASongFromPlaylist(Song * song)
+void deleteASongFromPlaylist(const Song * song)
 {
 	int i;
 

src/playlist.h

@@ -101,7 +101,7 @@ enum playlist_result savePlaylist(const char *utf8file);
 
 enum playlist_result deletePlaylist(const char *utf8file);
 
-void deleteASongFromPlaylist(Song * song);
+void deleteASongFromPlaylist(const Song * song);
 
 enum playlist_result moveSongInPlaylist(int from, int to);