OGL30 renderer: Don't flush if trying to rebind the current surface
OGL30 renderer: Don't flush if trying to rebind the current surface

This saves quite a large number of gl calls, as apparently trying to
setSurface() the already-bound surface happens quite often :)

AndO3131/OpenApoc,FranciscoDA/OpenApoc,pmprog/OpenApoc,Istrebitel/OpenApoc,AndO3131/OpenApoc,ShadowDancer/OpenApoc,FranciscoDA/OpenApoc,pmprog/OpenApoc,steveschnepp/OpenApoc,steveschnepp/OpenApoc,FranciscoDA/OpenApoc,ShadowDancer/OpenApoc,Istrebitel/OpenApoc,AndO3131/OpenApoc