general SIMD acceleration for angles+dihedrals

Implemented SIMD intrinsics for angle potential and pbc_dx.
Changed SSE2 intrinsics to general SIMD using gmx_simd_macros.h.
Improves performance significantly, especially with AVX-256
and reduces load imbalance, especially with GPUs.

Change-Id: Ic83441cce68714ae91c6d5ca2a6e1069a62cd2ae
Merge "general SIMD acceleration for angles+dihedrals" into release-4-6