glx/test: meson: assorted include fixes

Swap '..' with the symbolic inc_glx and add glproto as dependency. That
will pull the correct include, effectively fixing the tests on macOS.

Fixes: a47c525f ("meson: build glx")
Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Dylan Baker <dylan@pnwbakers.com>
(cherry picked from commit f331419f)
[Juan A. Suarez: resolve trivial conflicts]
Signed-off-by: Juan A. Suarez Romero <jasuarez@igalia.com>

Conflicts:
	src/glx/tests/meson.build