"Interior. Leather Bar." is a sly conceptual coup d’art and a deeply sincere exploration of masculinity and its discontents, with a little hot sex thrown in. The movie’s ostensible point of departure is 40 minutes of graphic footage of S-and-M that the director William Friedkin was forced to edit out of “Cruising,” his 1980 thriller with Al Pacino, to avoid an X rating. Inspired by what they rather cryptically term the mythology of “Cruising,” Mr. Franco and Mr. Mathews have set out to reimagine this excised material.