Fix T44046: Cycles speed regression in 2.74 (CPU only)
Fix T44046: Cycles speed regression in 2.74 (CPU only)

Issue was caused by MSVC not being able to optimize some code out in the same
way as GCC/Clang does, so now that parts of code are explicitly unfolded in
order to help compilers out.

This makes speed loss much less drastic on my laptop. That's probably as good
as we can do with MSVC without investing infinite amount of time looking trying
to workaround the optimizer.

tangent-opensource/coreBlackbird,tangent-opensource/coreBlackbird,tangent-opensource/coreBlackbird