Cotillard did triple duty at the New York Film Festival Sunday to promote ‘Two Days, One Night,’ which had its U.S. premiere. (The film is Belgium’s submission for best foreign film.) At 1, in jeans and a casual but chic top, Cotillard participated in a Q&A for a standing-room crowd. At 3 she changed into Dior and walked across the street to Alice Tully Hall and joined the Dardenne Brothers as they introduced ‘Two Days, One Night’ to a sold out audience, and afterward participated in a Q&A.