[OpenSCAD] Add piecewise helix for OCCT < 7.5

Address a hang when using older versions of OCC to create a rotated
extrusion. This approximates the auxilliary spine as set of line
segments formed from the helix, rather than using the helix directly.

src/Mod/OpenSCAD/OpenSCADFeatures.py

@@ -431,7 +431,17 @@ def createGeometry(self,fp):
                         left_handed = True
                     else:
                         left_handed = False
+
                     auxiliary_spine = Part.makeHelix(pitch, height, radius, 0.0, left_handed)
+
+                    # OCC versions before 7.5 had a problem with using a helix as the auxilliary spine, so approximate
+                    # it piecewise
+                    occ_version = Part.OCC_VERSION.split(".")
+                    if int(occ_version[0]) <= 7 and int(occ_version[1]) < 5:
+                        num_points = int(max(3,num_revolutions * 36)) # Every ten degrees is adequate
+                        wire = auxiliary_spine.Wires[0]
+                        points = wire.discretize(Number=num_points)
+                        auxiliary_spine = Part.makePolygon(points)
 
                 faces = [lower_face,upper_face]
                 for wire1,wire2 in zip(lower_face.Wires,upper_face.Wires):