18 December 2014 Last updated at 15:30 GMT Pakistan is marking three days of mourning following the Taliban attack on a school in Peshawar on Tuesday. Prayer vigils are being held nationwide, with Pakistani embassies across the world lowering their flags to half-mast and opening books of condolences. The BBC’s Shaimaa Khalil spoke to attack survivor Aqif Azeem – one of several pupils who have…