[Xmonad] darcs patch: add pureMessage.

[Don Stewart]

droundy:
> Dons suggested this, and it sounded like a nice idea to me.
> Alas, only one user in core, but several contrib modules could
> use it.  I'm not sure how useful this will be for quickchecking,
> as we'll need to create an Arbitrary instance for an existential
> type, which means we'd need some sort of trickery to create tests
> relevant to each layout.
> 
> David
> 
> Fri Oct  5 10:05:53 EDT 2007  David Roundy <droundy at darcs.net>
>   * add pureMessage.
> 


Applied.