<AWT Dev> Add mutter as a window manager.

[Denis Lila]

Hi.

We have this bug where, using the mutter window manager,
if one moves netbeans anywhere on the screen except at
the top left and then maximizes it, clicking is broken.
This is because after maximizing the position of the
XDecoratedPeer is not updated. On Metacity and some other
WMs this is done using a WM specific workaround.

I've added Mutter as a WM, and this webrev fixes the problem:
http://icedtea.classpath.org/~dlila/webrevs/mutterBug/

Any comments are much appreciated.

Thank you,
Denis.