[Xmonad] darcs patch: clean up TwoPane to work on Stacks as it ought.

Hi all, Here's a cleanup of TwoPane to make it properly work with the new Stack input. It is now a pure Layout, which is much prettier. David Tue Jun 19 08:09:28 PDT 2007 David Roundy * clean up TwoPane to work on Stacks as it ought.