Overhauled bouncegrid light splatting for performance reasons - instead of a series...

Overhauled bouncegrid light splatting for performance reasons - instead of a series of radial dots being accumulated in the texture, it is spherical distance from line segment calculations performed at each pixel, optimized to process pixels in order (filtering down the list of splat paths in each loop).  This is a big framerate increase (as raytracing was not the bottleneck at all), and could be threaded in theory.

This required rebalancing the way that spacing interacts with quality, and the conespread parameter has been eliminated (as measuring distance to a non-uniform capsule seems especially challenging, but maybe that could be added back someday), so all parameters have changed a bit.

git-svn-id: svn://svn.icculus.org/twilight/trunk/darkplaces@12491 d7cf8633-e32d-0410-b094-e92efae38249