Planning add-window-matcher extension

[Teika Kazura <teika lavabit com>]

Hi. In order to make keymap-trans support saner, I'm planning
an extension for add/remove-window-matcher functions.

Currently, the usage is: 

(add-window-matcher 'WM_NAME "^Terminal$"
        '( new-viewport . t )
        '( fullscreen . t ) )
(From Chris' rc.)

What I plan is:
(add-window-matcher 
  '((WM_NAME "^Terminal$")
    (WM_CLASS "SuperSpecialUser"))
      properties... )

The old grammar remains supported, too, and it's documented that
there's the spec change.

It may break feature freeze, but it's tiny, bug-free by nature, so
must be ok.

Teika (Teika kazura)