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/window.c

@@ -366,6 +366,7 @@ CreateRootWindow(ScreenPtr pScreen)
     WindowPtr	pWin;
     BoxRec	box;
     PixmapFormatRec *format;
+    FocusSemaphoresPtr sem;
 
     pWin = (WindowPtr)xalloc(sizeof(WindowRec));
     if (!pWin)
@@ -484,6 +485,7 @@ CreateRootWindow(ScreenPtr pScreen)
 		
     if (disableSaveUnders)
 	pScreen->saveUnderSupport = NotUseful;
+
     return TRUE;
 }