[IronPython] Running Scripts/generate.py on CPython

[Seo Sanghyeon]

Scripts/generate.py has a comment: "TODO: does it make sense to run
this under CPython?". I think so. The following is how I did that:

1. Delete "import nt" at the top. It is imported later anyway.
2. Change root_dir and source_directories. (Because source layout is
different, but change is easy.)
3. Uncomment lines under "TODO: does it make sense..."
4. Define basename as os.path.basename and System.IO.Path.GetFileName
just like isdir. Use it later.

Maybe change 1 and 4 can be made on IronPython?

Also change code_text += "\n" to "\r\n" if you want to avoid line
ending difference.

-- 
Seo Sanghyeon