(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.

openttd_vs80.vcproj

@@ -345,6 +345,10 @@
 				RelativePath=".\mixer.c"
 				>
 			</File>
+			<File
+				RelativePath=".\music.c"
+				>
+			</File>
 			<File
 				RelativePath=".\namegen.c"
 				>
@@ -654,6 +658,10 @@
 				RelativePath=".\mixer.h"
 				>
 			</File>
+			<File
+				RelativePath=".\music.h"
+				>
+			</File>
 			<File
 				RelativePath=".\network.h"
 				>