Function axis_angle_to_quat 

pub fn axis_angle_to_quat(aa: [f32; 4]) -> [f32; 4]

Converts axis-angle [ax, ay, az, angle] to quaternion [w, x, y, z].

The angle is in radians. A zero-length axis or zero angle produces the identity quaternion [1, 0, 0, 0].