Enable c++11 for pugixml cmake build
Enable c++11 for pugixml cmake build

This is required to enable the 'long long' types

ShadowDancer/OpenApoc,pmprog/OpenApoc,Istrebitel/OpenApoc,Istrebitel/OpenApoc,ShadowDancer/OpenApoc,FranciscoDA/OpenApoc,steveschnepp/OpenApoc,pmprog/OpenApoc,steveschnepp/OpenApoc,FranciscoDA/OpenApoc,FranciscoDA/OpenApoc