vim: Update to patchlevel 205 and add PYTHON option

When python is built with DEBUG, vim fails to build. In fixing this
case, note that vim will now fail to build if python or vim is build
with DEBUG and the other isn't.

This also highlighted that python support is being kludged. The
PYTHON2 and PYTHON3 options have been combined into a single PYTHON
option that builds with the default python. Consequently, it is no
longer possible to build vim with both py2 and py3 support. I can't
name any modern high-usage python-based plugin that requires 2.7,
so hopefully this only messes up things for a very small minority.

Thanks to koobs for the prompt to combine these options. I've been
wanting to do this for a while now.

PR: 243606
Submitted by: novel