Made -testHitTestInWindowLayer retrieves the visible screen frame with  -rootWindowFrame until -[NSScreen visibleFrame] works better on GNUstep.
Made -testHitTestInWindowLayer retrieves the visible screen frame with 
-rootWindowFrame until -[NSScreen visibleFrame] works better on GNUstep.


git-svn-id: 0833b781a6984bca00fd44c5b8a33a6c879c84c9@5923 7b3f36aa-e6db-49c1-8b4c-66eac1997e64

etoile/EtoileUI,etoile/EtoileUI