Bezier Library for OpenScad

See http://github.com/uplake/BezierScad

Updated 5/10/13--fixed triangle winding in centered BezWall; use polyhedron for variable-height BezArc.

I wanted a bezier library that could handle an arbitrary number of control points. When working on thingiverse.com/thing:77586, I also wanted to rotate extrude a "wall" defined by a bezier path and a width.

BezWall is the workhorse function. The "ctlPts" parameter accepts between 1-8 bezier control points.

The parameters "width" and "heigh