Moving an actor with a ClutterDeformEffect applied flickers because
the depth_testing, setting the depth testing test function to
COGL_DEPTH_TEST_FUNCTION_LEQUAL fixes the problem.
Fixes https://gitlab.gnome.org/GNOME/mutter/issues/507
In cogl use cogl-config.h and in clutter use clutter-build-config.h. We
can't use clutter-config.h in clutter because its already used and
installed.
https://bugzilla.gnome.org/show_bug.cgi?id=768976
