[Xmonad] darcs patch: add SimpleStacking module to make Combo and Tabbed wor...

This is an amend-recorded version of the SimpleStacking patch, which fixes a (slow) leak and a warning. David Thu Jun 21 08:15:24 PDT 2007 David Roundy * add SimpleStacking module to make Combo and Tabbed work together. WARNING! This change will break existing Tabbed configurations. The problem is that there is no way within a Layout's "doLayout" to safely modify the layout itself. This makes LayoutHooks fragile, and more to the point, makes SimpleStacking fragile, so we can't safely define a tabbed' = simpleStacking . tabbed A workaround would have been to duplicate the tabbed code, but I'd rather leave the ugliness and get this fixed.