shiftPrevScreen and shiftNextScreen, to make CycleWS consistent
shiftPrevScreen and shiftNextScreen, to make CycleWS consistent

darcs-hash:20071231171609-c9905-843656222b29cf2f40922b243d78be02608a9a8a

yzhou61/xmonad-contrib,yzhou61/xmonad-contrib,yzhou61/xmonad-contrib