Add some gpu culling feature

[happydpc]

Now I am working with some massive huge model, it will draw too many objects. So I hope this can implement some gpu culling like this in bgfx:

[(https://github.com/bkaradzic/bgfx/tree/master/examples/37-gpudrivenrendering)]

[polymonster]

Hi, I am interested in these kind of features its just finding the time to implement it.. which platform are you working on so I could prioritise it?

[happydpc]

Hi, I am interested in these kind of features its just finding the time to implement it.. which platform are you working on so I could prioritise it?

I am working with windows 10 VS 2017. Thank you. Very good library.