The 47th entry in the “X-Men” franchise (just kidding, but it’s easy to lose track) stays with the younger series of actors playing the Marvel mutants. You know, the ones with James McAvoy and Michael Fassbender as Charles Xavier and Magneto, not Patrick Stewart and Ian McKellen.But “X-Men: Apocalypse” opens a lot further back in time, in 3,600 B.C.