[xmonad] Determining layout based on display properties

[Nathaniel Filardo]

I wrote a module to do exactly that.  I'm not entirely happy with it
(and patches are definitely thoughtfully considered), but it's
available at

> https://github.com/nwf/xconfig/blob/master/xmonad/lib/XMonad/Layout/SLS.hs

Hope that helps.
--nwf;