[Migrants rest next to buses as they wait to cross the Greek-Macedonian border near the village of Idomeni]By Fedja Grulovic POLIKASTRO, Greece (Reuters) - Hundreds of migrants set out on foot along a major north-south highway in Greece on Tuesday, heading north for Macedonia after being stranded for days by farmer and taxi driver protests on either side of the frontier. At least 80 buses packed with migrants, many of them women and children fleeing the war in Syria, were backed up 10 km (6.2 miles) short of Greece's border with Macedonia, halted by police. Then, with patience running out, hundreds of migrants disembarked from their stationary buses and blocked the road, sitting on the tarmac and chanting "Macedonia, Macedonia!" One group set out on foot, according to a Reuters cameraman at the scene.