[ET Trac] [Einstein Toolkit] #1708: Add autoconf detection for #pragma omp simd

#1708: Add autoconf detection for #pragma omp simd -------------------------+-------------------------------------------------- Reporter: eschnett | Owner: Type: enhancement | Status: new Priority: major | Milestone: Component: Cactus | Version: development version Keywords: | -------------------------+-------------------------------------------------- This pragma simd-vectorizes a loop. It is part of OpenMP 4.0. Unfortunately, not all compilers support it. We need to add an autoconf rule.