Taskbar now simply asks the WindowServer to popup a window menu when right
clicking on a taskbar button.
This patch also implements the "close" menu item, and furthermore makes the
window menu show up when you left-click a window's titlebar icon. :^)
Also run it across the whole tree to get everything using the One True Style.
We don't yet run this in an automated fashion as it's a little slow, but
there is a snippet to do so in makeall.sh.
