[Xmonad] darcs patch: fix leak in Combo.

Hi all, Here is a pretty important fix to Combo. Fortunately, I doubt anyone but myself has been using this, so I'm probably the only one with vastly bloated memory use in my X server. It does make me wonder if there's a better design we could use, though. :( David Sat Jun 16 12:10:52 PDT 2007 David Roundy * fix leak in Combo. We leaked decorations, since UnDoLayout wasn't passed to the actual layouts that had decorations attached. :(