The integrationTest function takes a new optional argument whether the
test supports a Wayland Only mode. If that's the case the test is
compiled twice, once (as always) as "foo" with XWayland support and
once as "foo_waylandonly" without XWayland support.

This way we can ensure that our code always supports both modes. The
tests found multiple issues. At the moment fast running tests are
sporadically crashing on tear down. This needs further investigation.