Compatibility reporting

[Michael-F-Bryan]

It'd be really nice to have a tool that shows how compatible this implementation is with the main OpenSCAD project. Ideally we'd have a large set of *.scad files and see how many we can parse or evaluate.

Some ideas:

• The tests/data/ directory in the main openscad/openscad repo
• The various parts in nophead/NopSCADlib

This would also make it easy to see which functions or language constructs we still need to implement.