[Xmonad] darcs patch: change Dmenu functions to return IO/X (Maybe String)

Sat Oct 6 03:09:59 EDT 2007 Devin Mullins * change Dmenu functions to return IO/X (Maybe String) dmenu exits with code 1 when you hit Escape, and I wanna create a contrib that takes advantage of that. This required changes in four contribs (Commands, DirectoryPrompt, ShellPrompt, and WorkspaceDir), and might require changes in users' Configs. Also, I'm not sure some of the changes I made to the client code are very Haskelly. Would appreciate input there.