This widget is automatically included in GStatusBar, but can be added in
any other place, too. When clicked (with the left button), it initiates a
window resize (using a WM request.)
In this patch I also fixed up some issues with override cursors being
cleared after the WindowServer finishes a drag or resize.
My needs are really quite simple, so I'm just going to add what I need
as I go along. The first thing I needed was a simple box layout with
widgets being able to say whether they prefer fixed or fill for both
their vertical and horizontal sizes.
I also made a simple GStatusBar so FileManager can show how many bytes
worth of files are in the current directory.
