Not every 25-year-old filmmaker comes out fully formed, as Orson Welles did with Citizen Kane. Xavier Dolan, born in 1989 and already with five features as a director, is less protean in his talent, less wise, less articulate, than wunderkind Welles. But there’s something urgent going on with this French-Canadian director, and youth has a great deal to do with it. The success of his 2014 Cannes prizewinner Mommy has prompted a proper U.S. release for Tom at the Farm, a sinister 2013 film directed by and starring Dolan (from a play by Michel Marc Bouchard). The opening half-hour sets up expectations for a familiar kind of social drama, circa 1998.