devel/simde: Header-only library for SIMD intrinsics

The SIMDe header-only library provides fast, portable implementations
of SIMD intrinsics on hardware which doesn't natively support them,
such as calling SSE functions on ARM. There is no performance penalty
if the hardware supports the native implementation (e.g., SSE/AVX runs
at full speed on x86, NEON on ARM, etc.).

(bacon)