Function safe_arch::addsub_m128

#[must_use]pub fn addsub_m128(a: m128, b: m128) -> m128

This is supported with target feature sse3 only.

Alternately, from the top, add a lane and then subtract a lane.

let a = m128::from_array([10.0, 20.0, 30.0, 40.0]);
let b = m128::from_array([100.0, 200.0, 300.0, 400.0]);
let c = addsub_m128(a, b).to_array();
assert_eq!(c, [-90.0, 220.0, -270.0, 440.0]);