PerWorkspace: reimplemented using runLayout
PerWorkspace: reimplemented using runLayout

This way we have a Xinerama safe PerWorkspace and the emptyLayout
method for free.

darcs-hash:20080222175954-32816-97e4fc1140aa66ead879df019af3f091579251ab

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