Combo.hs: use case instead of non-standard pattern matching.
Combo.hs: use case instead of non-standard pattern matching.

Also uses fmap/maybe instead of do/case, which makes the code look a little
cleaner (imo).
Please note that I've only been able to test this briefly, but it seems to be
working like it's supposed to.

darcs-hash:20070620112805-ea16c-d246e45889110c7f28da80adbcfc968139f77130

kmels/xmonad-launcher,kmels/xmonad-launcher