cmd: Stripped down version of Python 3.3 cmd.py - #4

So, is this really written from scratch or edited from CPy's cmd.py? For the latter case, I tried to start with committing CPy module verbatim, and then apply changes in the next commit - so it was easy to see which exact changes were applied wrt to CPython version. I'd appreciate if you could do that, as if I try to do it, it will be hard to preserve your authorship.

And regarding setup.py, that's intended to be auto-generated from metadata.txt using make_metadata.py script in the root of repo.

OK - this was started with CPy's cmd.py. I'm happy to rework the PR to be the original CPy version and then do a changeset from there.

I'll create a metadata.txt file and generate setup.py from it.

I added the cmd.py from 3.4 (or 3.3 - they're both the same) and then did a separate commit for the changes.

Merged with minor typo fixes.

Also pushed on PyPI.