Commit 58930: OSL performance increase

Just from the mailing list, OSL texture performance has been improved be 10-25%

Hi fellow cyclists,

I did a little experiment to try and improve the performance of cycles/OSL in scenes that use image textures. I tested the Barcelona scene from ba.org and tried a bit of an ugly hack to cache the OIIO perthread info.

I only have an ancient macbook pro here with me on holiday and would need to investigate further but initial results are a ~ 15% improvement on overall render time on this scene.

I expect the improvement to be bigger for machines with more cores but I cannot test that from here.

I attached the patch

-Martijn Berger

It may only have such a big performance for OSX, though probably at least a little for Windows and Linux