[OpenSCAD] Importing DXF Files

[Alan Cox]

> The problems start when the imported STL is not manifold, in which case
> openscad finds itself quite unable to /export/ but this is not openscad's
> fault, it was never designed to handle non-manifold meshes.

These were valid manifold meshes that were *produced* by OpenSCAD. It
seems OpenSCAD can't properly handle sharp edges in an STL file (or CGL
can't)

Alan