Aamir Khan, the star of “Dangal, ” is as formidable and celebrated a movie star as India has going. Two years ago, he played the lead character in “PK, ” a sci-fi comedy about an alien who visits earth and points out everything wrong with it; the film went on to become the top-grossing movie in Bollywood history. Fifteen years ago, Khan starred in “Lagaan, ” the transporting colonial cricket-match musical that was the last Indian film to be nominated for an Academy Award. In “Dangal”(the title means “Wrestling”), Khan has aged nicely. He keeps his short muscular body poised, and his cropped hair sets off jutting ears, plunging eyebrows, and a serene scowl that almost never leaves his face; he looks like a jock version of Salman Rushdie. Yet within that tight-lipped mask, he finds a hundred ways to communicate emotion.