Remove some MAX* #defines that never get used.

include/misc.h

@@ -87,10 +87,7 @@ extern unsigned long serverGeneration;
 #define MAXSCREENS	16
 #endif
 #define MAXCLIENTS	256
-#define MAXDITS		1
-#define MAXEXTENSIONS	128
 #define MAXFORMATS	8
-#define MAXVISUALS_PER_SCREEN 50
 
 typedef unsigned long PIXEL;
 typedef unsigned long ATOM;