His novel “1984” captured the tactics of totalitarianism back in 1949. A startling new documentary from Raoul Peck looks at Orwell’s life.“The opinion that art should have nothing to do with politics is itself a political attitude,” George Orwell wrote in 1946, a year after the end of the World War II. That line appears early in “Orwell: 2 + 2 = 5,” an essayistic documentary from Raoul Peck that surveys its title subject’s life and work, using them as a lens to explore authoritarian power in the past and the present. Densely packed, the movie is a whirlwind of...