Add agressive event type checking.

Best to FatalError if a wrong event comes in. At least that forces me to fix
it really quickly.

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

dix/events.c

@@ -2247,6 +2247,8 @@ DeliverDeviceEvents(WindowPtr pWin, InternalEvent *event, GrabPtr grab,
     xEvent *xE = NULL;
     int rc, count = 0;
 
+    CHECKEVENT(event);
+
     /* XXX: In theory, we could pass the internal events through to everything
      * and only convert just before hitting the wire. We can't do that yet, so
      * DDE is the last stop for internal events. From here onwards, we deal
@@ -2527,6 +2529,8 @@ CheckMotion(DeviceEvent *ev, DeviceIntPtr pDev)
     WindowPtr prevSpriteWin;
     SpritePtr pSprite = pDev->spriteInfo->sprite;
 
+    CHECKEVENT(ev);
+
     prevSpriteWin = pSprite->win;
 
     if (ev && !syncEvents.playingEvents)