There’s a short anxious scene in the new film “The Hunger Games,” when its 16-year-old heroine, Katniss Everdeen (Jennifer Lawrence), races through a deep, dark forest, falls down a hill and rolls and rolls only to rise up and thrust herself again into the unknown. Katniss, the lethally tough linchpin from Suzanne Collins’s trilogy turned rather less imposing film heroine, is a teenage survivalist in a postapocalyptic take on a familiar American myth. When she runs through that forest, and even when she falls, there’s something of the American frontiersman in her, as if she were Natty Bumppo reborn and resexed.