Yet another thread library for OpenSCAD

This is yet another OpenSCAD thread library, and it was more fun to write it than to find a library that did exactly what I wanted. It's designed to be fairly fast: it generates the whole thread polyhedron as a single piece.

Thread profile is completely flexible. You can specify a counterclockwise polygon of 2D points for the profile or you can use ISO thread profiles.

There are two modules exposed:
`rawThread(profile, d=diameter, h=height[, lead=lead, $fn=segmentsPerRotation])`: draw t