Finally merging the performance branch

It’s finally time to merge the performance branch. I basically redesigned the whole renderer and rasterizer around high resolution workloads, where it would still choose the old high-poly paths where they were faster.

Even snuck in some SSE2 SIMD code (picture), although I will probably be switching to a dispatch SIMD library like Google’s Highway. Not entirely sure it will be Highway or even if I will do that yet, that depends on the code complexity and before/after benchmarks.