A bunch of people born in the 1970s discuss two films from that decade about young people coming of age: 1973’s “American Graffiti” and 1979’s “Breaking Away.” The first is a film (set in 1962) featuring young people driving around a northern California town on the last night of summer before reality sets in; the second is about young people riding bikes (and swimming in a quarry) in Indiana. The first comes from the future director of “Star Wars”; the second comes from the future director of “Krull”. Both are full of faces you will recognize. And both have interesting things to say about being young and the prospect of growing up.