wayland: Support for QtWayland windowmanager

Add support for the windowmanager protocol from QtWayland.

This handles sending the SDL_QUIT event when the window
manager sends the corresponding qt_windowmanager.quit event.

The files wayland-qt-windowmanager.{c,h} are auto-generated
from the XML definition src/extensions/windowmanager.xml in
qtwayland (git://gitorious.org/qt/qtwayland.git).