generate_torus: r_outer and r_inner parameters are misnamed

The parameters r_inner and r_outer to generate_torus don't refer to the outer and inner radius of the torus. They instead should be renamed r_major and r_minor because they refer to the major/minor radii of the torus, which are pictured below. r_minor is the radius of the tube and r_major is the distance from the center of the torus to the center of the tube.

^ (from wikipedia)