email.internal: Add pristine from CPython 3.3.3.

This dist-package hosts few "package private" modules with names starting
with "_". Maybe this is not the best grouping, but having a separate
dist-package for each such module is a bit verbose.
email.internal: _policybase.py: Short-circuit metaclass and __doc__ stuff.
email.internal: Add metadata.
email.message: Add email.iterators module to dist-package.

It's import by email.message and small, so makes no sense to have separate
dist-package for it.
csv: Add dummy module.
shelve: Add dummy module.