ICC 15.0.2 bug
calc_dr_x_xp_simd compiles incorrectly with ICC 15.0.2. It is almost guaranteed a compiler bug not a GROMACS error (the problem goes away at lower optimization or when adding a printf). Already reported to Intel. So far we weren't able to come up with a local work-around. If we can't find one before the release we should add an error to cmake.