[Ayatana] Put a resize widget in the title bar

[Remco <remco47@xxxxxxxxx>]

With the new theme, the resize border has been reduced to 1 pixel,
making it annoyingly difficult to resize a window. Some solutions have
been proposed, such as always requiring a status bar with a resize
widget, or doing some magic with the borders to make them act like
they are bigger than 1px. The easiest solution has--as far as I
know--been overlooked: use the title bar. We don't use the right side
of the title bar at the moment. Eventually, it will fill with
windicators. How about we put one in there for every window that can
be resized: a dotted resize handle. A mockup is attached.

-- 
Remco

Attachment: resize-widget-in-titlebar.png
Description: PNG image