Remove the MacOSX focusing-click mouse-move hack.

It no longer works with the new LWJGL as the main game frame is
no longer an AWT window.

So: the issue now returns that this was trying to solve:
If you refocus the window with a click; don't move the mouse
a single pixel; then click again, the click location will be
at the place where the mouse was when the window originally lost focus.

I'm leaving the hack in here, commented out, while I look for another fix.
It seems we don't need to throw away the focusing click anymore.

Something's doing it for us, at least here on Mac.
I'll check it out on other platforms...