Function safe_arch::addsub_m128d

#[must_use]pub fn addsub_m128d(a: m128d, b: m128d) -> m128d

This is supported with target feature sse3 only.

Add the high lane and subtract the low lane.

let a = m128d::from_array([10.0, 50.0]);
let b = m128d::from_array([100.0, 500.0]);
let c = addsub_m128d(a, b).to_array();
assert_eq!(c, [-90.0, 550.0]);