When twist-extruding, call new twist_extrude_face() stub for each face.
Implement twist_extrude_face in terms of twist_extrude_wire stub.
Add is_inner_wire_of_face().
Use is_inner_wire_of_face for condition in twist_extrude_face.
Allow from_ruby<gp_Pnt> to accept 2D points (with z=0).
Use 3D, not 2D, curves in polygon_render().
Remove template parameters from make_wire_from_path (no longer necessary).
Pass twist parameter correctly in HelicalGear.initialize.
Implement twist_extrude_wire().
Add missing call to BRep_Builder::MakeCompound() so
linear_extrusion_render doesn't crash.
Fix helical gears

 * Specify helix_angle in radians
 * Space helical gears correctly in herringbone gear