[Xmonad] darcs patch: add DragPane.

This is basically like TwoPane, except that there's a little gap between the panes which you can grab and drag, so you can have finer-resolution control over the splitting. It also works nicely with Combo, so you can now have almost ion-like control over your layout. David Mon Aug 13 07:40:07 PDT 2007 David Roundy * add DragPane.