GENEVA (Reuters) - The United Nations refugee chief called on Friday for a "massive resettlement" of Syrian and other refugees within Europe, to distribute many hundreds of thousands of people before the continent's asylum system crumbles.Antonio Guterres, U.N. High Commissioner for Refugees, welcomed an agreement for the European Union's border agency Frontex to boost its presence in Greece to help register, screen and interview asylum seekers, but said it was not enough.