trivial: Add a self test for as_app_subsume()
trivial: Add a self test for as_app_subsume()

ximion/appstream-glib,kalev/appstream-glib,superm1/appstream-glib,ximion/appstream-glib,hughsie/appstream-glib,ikeydoherty/appstream-glib,hughsie/appstream-glib,mitya57/appstream-glib,mitya57/appstream-glib,ikeydoherty/appstream-glib,superm1/appstream-glib,hughsie/appstream-glib,ximion/appstream-glib,kalev/appstream-glib