Benchmarking The New RadeonSI/Gallium3D Threaded Support

Xonotic was seeing some small but noticeable performance improvements.

Serious Sam 2017 was seeing little to no performance changes with the RadeonSI threaded code.

The good news from this testing in the Linux OpenGL tests executed was no performance regressions encountered. In a number of the games there were noticeable performance improvements but in the more GPU-demanding games the results were virtually the same. Percentage-wise some of my results weren't as significant as Marek's findings due to these tests being done with the faster Core i7 7700K. I'll next be working on some similar Linux gaming tests with Ryzen using these pipe context threading patches. Given these results so far, hopefully we will see this feature merged to Mesa 17.2-dev soon.