Increase the size of the bottom resize edge, and make the left-bottom and
right-bottom corners larger, and "L"-shaped, for easier gripping.
Rationale: Xfwm doesn't support magic window edges, so they need to be
larger in order to be clickable. 2px is too narrow for this.
Allow the top left and right pixels of maximized windows to be clickable
if there's a window button there, for greater Fitts's Law compliance. The
exception is the window menu button, which needs a minor hack to be sized
correctly.
Somewhat darker inactive button icons, to match window title text.
Add an SVG-based build system to allow colours to be changed easily.
Andrew Chadwick