EGL: X11 window output implemented

Much of the code from x11disp was borrowed from the Mesa demos, which were released under a free license, so legally it should be okay to use. But you really can't blame me, X11 is rocket science. I wish Wayland would happen sooner. KDE could have taken the initiative. But noo, we have to add more bling to our icons. Now Gnome are almost done, Ozone-Wayland is almost feature complete-ish, SDL is... erm... yeah....