Remove remaining sound stuff from WPrefs etc

Let's remove the configuration options about "sound" from
WPrefs (as it was never fully functionall anyway) and from
configuration files.

Remove also the xpm and tiff icons.

WindowMaker/Defaults/WMWindowAttributes.in

@@ -4,7 +4,6 @@
   Logo.WMClip = {Icon = clip.#extension#;};
   Dockit = {Icon = GNUstep.#extension#;};
   DockApp = {NoAppIcon = NO;};
-  WSoundServer = {Icon = sound.#extension#;};
   panel.Panel = {NoAppIcon = YES;};
   gmc.Gmc = {NoAppIcon = YES;};
   XTerm = {Icon = Terminal.#extension#;};