Improved error message on circular include.
Heaps of progress in port to windows.

The windows example works now for C/C++. The instructions for dmd
on windows are a bit thin, so I took out the D part of the example.

Most of the problems were to do with:
* Filename extensions.
* The windows copy command not being available as a file.
* Environment variables.
* Executable is in the filename instead of an attribute.