dix: reduce MDs and xtest pointers to 7 buttons by default.

MD's will soon be the union of all devices anyway. XTest pointers are only
for the core protocol XTest stuff, so 7 buttons (lmr + 4 wheel buttons)
should do.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

dix/devices.c

@@ -554,7 +554,7 @@ CoreKeyboardProc(DeviceIntPtr pDev, int what)
 static int
 CorePointerProc(DeviceIntPtr pDev, int what)
 {
-#define NBUTTONS 32
+#define NBUTTONS 7
 #define NAXES 2
     BYTE map[NBUTTONS + 1];
     int i = 0;