AVX2 alignment issues with MSVC

[tterribe]

The AVX2 code does not compile with MSVC: error C2719: 'value': formal parameter with __declspec(align('32')) won't be aligned.

We don't have an OD_SIMD_INLINE for MSVC, but according to Srinath Reddy at Microsoft, using __forceinline there does not solve the problem (both because MSVC reports the error before attempting to inline things and because inlining is not guaranteed, even with __forceinline).

We'll have to come up with some other way to address this problem.