This patch adds functionality to make use of recent XWayland patches for
emulating RandR resolution changes through the Wayland wp_viewporter protocol
For that a specific window property must be read and the emulated size sent via
X11 protocol to the respective client window.
This patch is WIP because I noticed structural problems that we have with the
current XWayland code. For one KWin is creating one too many parent windows to
work together with the new XWayland code.