Summary:
This diff adds 32-bit support for F14, so SSE and NEON
intrinsics can be used on x86 and arm architectures (rather than just
x86_64 and aarch64).  The portability fallback to std::unordered_map
and std::unordered_set is now used only when vector intrinsics are not
available, or on PPC.

Reviewed By: shixiao

Differential Revision: D8586283

fbshipit-source-id: 1c4d090e80381fe7ad071c3059b3cb242c04c9f7