WIP: xwayland: Disable the XTEST extension by default
Most features from the XTEST extension cannot work on Wayland, which can be misleading for applications which would (optionally) rely on that extension to implement some features.
Disable the XTEST extension by default to make it clear that XTEST is not supposed to work on Xwayland, so that X11 clients are not tempted to use it.
Using the standard command line option "+extension XTEST" can re-enable it at runtime, if really needed.
Signed-off-by: Olivier Fourdan ofourdan@redhat.com