(svn r5464) [Behaviour Fix] : When starting the game, the system will now verify the presence of music files in gm forlder.

A song can now be removed from the programmed list (in custom list 1 and 2) by clicking on it.
Added music.c[ch] files, to make it all a bit cleaner.
Now, the name of the gm file is associated with the title of the song.

Makefile

@@ -671,6 +671,7 @@ SRCS += misc.c
 SRCS += misc_cmd.c
 SRCS += misc_gui.c
 SRCS += mixer.c
+SRCS += music.c
 SRCS += music_gui.c
 SRCS += namegen.c
 SRCS += network.c