Fix the problem introduced by whoever thought that randomly changing ints

Fix the problem introduced by whoever thought that randomly changing ints

1998-04-14  Miguel de Icaza  <miguel@nuclecu.unam.mx>

	* gdk/gdkwindow.c (gdk_window_xid_at): Fix the problem introduced
	by whoever thought that randomly changing ints to unsigned int
	without reviewing the code was a good idea.  It is, btw not
	mentioned in the ChangeLog as usual, but I know it was not Elliot
	the culprit this time.