“Time passes. That’s for sure,” reads the pithy Eileen Myles epigram that launches "Grandma," Paul Weitz’s latest feature. Based on typical Hollywood fare, it could be hard to tell; unless one happens to be Meryl Streep or Richard Gere, life ends after 60, and if you happen to lack a Y chromosome it would seem to stop at least a decade earlier. But some of this might be changing.