input: fix up usage of button->down, used to be a bitmask, is now an array.

device->button->down used to be a 32-byte bitmask with one bit for each
button. This has changed into a 256-byte array, with one byte assigned for
each button. Some of the callers were still using this array as a bitmask
however, this is fixed with this patch.

Thanks to Keith Packard for pointing this out. See also:
http://lists.freedesktop.org/archives/xorg/2008-June/036202.html

dix/devices.c

@@ -1734,7 +1734,7 @@ DoSetPointerMapping(ClientPtr client, DeviceIntPtr device, BYTE *map, int n)
         if ((dev->coreEvents || dev == inputInfo.pointer) && dev->button) {
             for (i = 0; i < n; i++) {
                 if ((device->button->map[i + 1] != map[i]) &&
-                    BitIsOn(device->button->down, i + 1)) {
+                        device->button->down[i + 1]) {
                     return MappingBusy;
                 }
             }