Fixes to doctest driver

- Unicode fixes to doctest driver.
- For now doctest driver does not replace stderr with a SpoofOut.
  This makes debugging easier.
- Updated Makefile to force use of python3.
- Updated Makefile to use $(PYTHON) rather than just "python" in a
  couple places.
- Added a monkeypatching hack to rst.py to re-insert some functions
  that were deprecated and subsequently removed, but that are used by
  PIL.