[Xmonad] darcs patch: move Layout stuff into class (hokey first cut).

Hi all, Here's a patch that does a minimal conversion of Layouts moving into a Layout class. If this looks good to others, I'll see about converting XMonadContrib, maybe tomorrow (maybe not tomorrow). I'm not sure whether we want to include the OldLayout data structure I created. In the long run, I think not. In the short run, I think it's a good idea to include *some* sort of not-quite-trivial data structure in the class Layout in Main. David Fri Sep 14 17:59:59 EDT 2007 David Roundy <droundy@darcs.net> * move Layout stuff into class (hokey first cut).