“A Prophet,” a startling prison flick from French director Jacques Audiard, swept the Cesar awards — France’s version of the Oscars — over the weekend. The dark tale of a young, illiterate criminal who comes of age behind bars, took nine laurels, including best film, best actor (Tahar Rahim), best supporting actor (Niels Arestrup) and best director. A nominee for the foreign-language Oscar  in the USA, the film  opened here last Friday to strong reviews, including three and a half (out of four) stars from this critic, who discovered it at the 2009  London Film Festival.