In game loop only clear the surface just before the render
In game loop only clear the surface just before the render

As on some drivers (IE linux mesa) the first glCall waits for the next
buffer to be available, try to make sure they're all packed together.

This effectively allows better overlap between any outstanding renders
and the update() loop, increasing performance in these cases.

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