[Xmonad] darcs patch: add new LayoutHelpers module.

Here's a start of a sketch of a helper module to make it easier to write correct layouts, and also to insulate layout-writing code from changes to the Layout representation in XMonad core (e.g. so we can make it safe to modify layouts in doLayout, as LayoutHooks and SimpleStacking do). It's not very useful yet, but I still think this is suitable to go into the main XMonadContrib repo. David Fri Jun 22 07:29:50 PDT 2007 David Roundy * add new LayoutHelpers module.