By Dominic Evans BEIRUT (Reuters) - Syrian troops drove insurgents from central Homs on Monday, tightening their siege on remaining rebel bastions in the city, which links Damascus to the Mediterranean heartland of President Bashar al-Assad's Alawite sect. The military's gains in Khalidiya district follow a counter-offensive by Assad's forces, which have pushed back rebels around the Syrian capital and retaken several towns and villages near the border with Lebanon in the last few weeks. ...