dix: Rework Enter/Leave semaphore system.

Instead of a simple counter, use bits to keep track of which device is where
etc. When device enters a window (or sets focus), the bit matching the device
is set, when it leaves again, it is unset. If there are 0 bits set, then
Leave/Enter/Focus events may be sent to the client.

Same theory as before, but this should get around the insanity with
Grab/Ungrab special cases. Those cases are basically untested though.

dix/devices.c

@@ -224,8 +224,7 @@ EnableDevice(DeviceIntPtr dev)
             if (dev->spriteInfo->spriteOwner)
             {
                 InitializeSprite(dev, WindowTable[0]);
-                ((FocusSemaphoresPtr)dixLookupPrivate(&(WindowTable[0])->devPrivates,
-                    FocusPrivatesKey))->enterleave++;
+                ENTER_LEAVE_SEMAPHORE_SET(WindowTable[0], dev);
             }
             else if ((other = NextFreePointerDevice()) == NULL)
             {