xrRender: implement simple occlusion culling for particles on OpenGL

Слиты xottab-duty запросил слияние github/fork/eagleivg/gl_culling в xd_dev

Created by: eagleivg

On OpenGL renderer, performance significantly less than DirectX. One of the reasons is particles. This PR introduces a simple occlusion culling by particle distance check on OpenGL (rs_vis_dist * 100).