[Xmonad] darcs patch: fix usage info for LayoutScreens.

[Donald Bruce Stewart]

droundy:
> Resend of previously-amended patch.  It's good that you're fast Don...  :)
> 
> David
> 
> Fri Jun 22 06:26:18 PDT 2007  David Roundy <droundy at darcs.net>
>   * fix usage info for LayoutScreens.

Done.

-- Don