[Xmonad] darcs patch: make Layouts able to layout whatever they like.

Hi all, This is a minor generification that allows Layouts to be used to lay out things other than windows. It makes no code change in core xmonad (just types gain an additional parameter), and obviously doesn't change the total number of lines. I think it's an improvement that will be useful, but I also haven't yet written any code to make use of it. Patch to XMonadContrib to follow. Most of the contrib layouts (and all the core ones) are generic. David Tue Jun 19 08:08:16 PDT 2007 David Roundy * make Layouts able to layout whatever they like.