Work around ARM64 Windows SDK arm_neon.h quirk

Since the Windows SDK has an ARM32-only arm_neon.h, files including it
during ARM64 Windows builds need to be redirected to arm64_neon.h.

Instead of editing many files to include ARM64-Windows-specific ifdef
logic, this commit introduces an ARM64-Windows-specific version of
arm_neon.h that performs the needed redirection and lands earlier in
the header search path than the ARM32-only arm_neon.h.

Change-Id: Idc63947a238ca1bd0c479d8f4ad68950487947c6