Redefine WindowTable as a fixed array

Instead of xalloc'ing it every server generation. The array is always
the same size (MAXSCREENS), anyway.

Xext/mbufbf.c

@@ -47,6 +47,7 @@ in this Software without prior written authorization from The Open Group.
 #include "gcstruct.h"
 #include "inputstr.h"
 #include "validate.h"
+#include "globals.h"
 #include <sys/time.h>
 
 #define _MULTIBUF_SERVER_	/* don't want Xlib structures */
@@ -199,8 +200,6 @@ static Bool bufChangeWindowAttributes();
 static void bufClearToBackground();
 static void bufCopyWindow();
 
-extern WindowPtr *WindowTable;
-
 static Bool
 bufMultibufferInit(pScreen, pMBScreen)
     ScreenPtr pScreen;