[pygtk] Pygtk client side windows / offscreen windows example

[John Stowers]

Hi All,

I wanted to play with the new Gtk+ client-side windows stuff so I wrote
an example. It is a port of the example shipped in gtk-demo.

http://gist.github.com/280520

It works on Pygtk 2.16 (uses Gtk+ 2.18). Some ctypes magic was necessary
to use functionality that was not wrapped in 2.16.

I also created a bug to ensure that the necessary API is available in
the next Pygtk release

https://bugzilla.gnome.org/show_bug.cgi?id=607393

John