if a port needs 2.x then set MODPY_VERSION=${MODPY_DEFAULT_VERSION_2}.
This commit doesn't change any versions currently used; it may be that
some ports have MODPY_DEFAULT_VERSION_2 but don't require it, those
should be cleaned up in the course of updating ports where possible.
Python module ports providing py3-* packages should still use
FLAVOR=python3 so that we don't have a mixture of dependencies some
using ${MODPY_FLAVOR} and others not.
Upstream uses additional sphinx extensions to generate API docs for
files on readthedocs. The port only uses sphinx to generate manpages
which don't require these; to avoid updating and importing a chain
of dependencies for things which don't affect the end results in
this port anyway, I have patched them away.
