Death to Multibuffer extension

The rationale behind is because no sane application will use this when we have
modern APIs such DRI2. Besides, as a fact, xfree86 server has already
deprecated this extension in 1998:

    http://www.xfree86.org/3.3.6/isc7.html

Signed-off-by: Tiago Vignatti <tiago.vignatti@nokia.com>
Reviewed-by: Keith Packard <keithp@keithp.com>

hw/xfree86/dixmods/extmod/modinit.c

@@ -47,15 +47,6 @@ static ExtensionModule extensionModules[] = {
 	NULL
     },
 #endif
-#ifdef MULTIBUFFER
-    {
-	MultibufferExtensionInit,
-	MULTIBUFFER_PROTOCOL_NAME,
-	&noMultibufferExtension,
-	NULL,
-	NULL
-    },
-#endif
 #ifdef SCREENSAVER
     {
 	ScreenSaverExtensionInit,