[Xmonad] darcs patch: use a global IORef to keep list of urgent windows

[Don Stewart]

me:
> On Mon, Oct 29, 2007 at 10:08:32PM -0700, Don Stewart wrote:
> > me:
> > > Any other reason this isn't applied?
> > You expressed hesitation? :)
> Point. ;) Well, for the record, consider me un-hesitating. I'd still
> like input on those restart bugs, but they're orthogonal to the patch.

Oh, that's an issue -- now you've hidden state away in a module, how are
we going to get at it to serialise? This is why global state is bad.

If the state was threaded through lambdabot, again, we'd be able to
flush it out when restarting.

So now I'm more hesitant about encouraing refs for state -- its
inherently going to break serialisation/restart persistence.

-- Don