[Greek Prime Minister Tsipras, Spain's Prime Minister Rajoy, French President Hollande, Portugal's Prime Minister Costa, Cypriot President Anastasiades and Italy's Prime Minister Gentiloni after the Southern EU Countries Summit in Lisbon]By Axel Bugge LISBON (Reuters) - French President Francois Hollande said on Saturday the new U.S. government was encouraging "populism and even extremism", as he and fellow southern European leaders urged unity to face an increasingly uncertain world. "We have to stand together in Europe," Hollande said during the meeting in Lisbon. "What is at stake is populism.