Function safe_arch::duplicate_low_lane_m128d_s

#[must_use]pub fn duplicate_low_lane_m128d_s(a: m128d) -> m128d

This is supported with target feature sse3 only.

Copy the low lane of the input to both lanes of the output.

let a = m128d::from_array([1.0, 2.0]);
let b = duplicate_low_lane_m128d_s(a);
assert_eq!(b.to_array(), [1.0, 1.0]);