Add PEP-639 and PEP-753 metadata

BaseEventLoop: rename _owner to _thread_id

Python issue 22448: cleanup _run_once(), only iterate once to remove …

…delayed

calls that were cancelled.

Bump version in setup.py.

Release asyncio version 0.4.1, identical to CPython 3.4.0rc2.

Bump to version 0.3.1.

Set version to 0.2.1. Ready for PyPI.

Changes by Sonald Stufft to build pypi distros. Yay!