[xmonad] Patch to add new Layout message

[Daniel Wagner]

Excerpts from Mike Meyer's message of 2014-09-23 07:31:08 -0700:
> The Message is called "SplitMaster", and has no arguments. It sets the
> client count of the master pane to 1 if it's not currently 1, thus
> providing a quick way to get back to that setting. It setgs the client
> count for the master pane to 2 if it's currently 1, effectively making it a
> toggle between the two modes of a split master pane and an full size master
> pane.

Can this be done entirely from the configuration? For example, a
low-tech solution would be to simply have two Tall layouts in your
layout hook (one with one master pane and one with two master panes) and
a keybinding that toggles between them, e.g. using
X.A.CycleSelectedLayouts [1].

I recognize that this is not *identical*, but perhaps it's close to your
needs and doesn't require changes xmonad's core.
~d

[1] http://hackage.haskell.org/package/xmonad-contrib-0.11.3/docs/XMonad-Actions-CycleSelectedLayouts.html