You just have to scan the spandex bulges in “The Avengers” to see that superhero movies remain a big boys’ club, with few women and girls allowed. Yes, there are female superheroes on screen, like Jean Grey from the “X-Men” series, but they tend not to drive the stories, while female superheroes with their own movies never dominate the box office. Most women in superhero movies exist to smile indulgently at the super-hunk, to be rescued and to flaunt their assets, like Scarlett Johansson’s character in “The Avengers,” whose biggest superpower, to judge by the on- and off-screen attention lavished on it, was her super-rump.