Really prevent changing to developer mode for non-developers.

	* glom/frame_glom.cc: on_menu_developer_developer(): Actually use the
	result of Privs::get_user_is_in_group().
	* tests/test_selfhosting_new_from_example_operator.cc: Test this
	same function here, though this test currently fails anyway.
	Really prevent changing to developer mode for non-developers.
	This fixes bug #669043 (alien)