ANKARA, Jan 6 (Reuters) - Countries around the world must do more to help Syria's neighbours cope with the millions of people who have fled the civil war, the U.N. High Commissioner for Refugees Antonio Guterres said on Tuesday. Over 3 million Syrians have arrived in Turkey, Leba**n, Jordan and Iraq during Syria's nearly four year war. Many **w live in abject poverty as a**ther winter bites. Leba**n, which has the highest per capita concentration of refugees, enforced new immigration controls along its Syrian border on Monday to try to stem the flow of people. ...