Mergining libtrianlges

Someone messaged my awhile ago asking to have my libtriangles relicensed under the lgpl, so they could include it in MCAD. That never happened, so here's my pull request. Let me know if I need to do anything else to the file, like explicitly mention the author or license in the file.

I also included a folder called "examples". inside is "example.libtriangles.scad". If you don't want the folder, I can move it into the main folder.