MFH: r407273 mail/py-pyspf: Fix dependencies (missing & incorrect)

Revision 404778 [1] modified py-pyspf to only use dns/py3dns instead
of conditionally using dns/py-dns and py-py3dns depending on whether
Python 2.x or 3.x was being used.

dns/py-py3dns is a Python 3.x *only* package, but the port does not
currently [2] limit itself to USES=python:3.0+.

This results in errors for all dependent ports of py-pyspf when
Python 2.x is used, which was reported for
mail/postfix-policyd-spf-python. [3]

pyspf's README notes the following requirements:

This package requires PyDNS (or Py3DNS for running with Python 3) and
either the ipaddr or python3.3 and later

This package requires authres from either pypi or
http://launchpad.net/authentication-results-python to process
and generate RFC 5451 Authentication Results headers.

The spf module in this version has been tested with python3.2 and does
not require using 2to3.

Accordingly, this change:

• Reverts to conditional RUN_DEPENDS on dns/py-dns or py-py3dns depending on whether Python 2.x or Python 3.x is being used.
• Adds authres to RUN_DEPENDS
• Adds a conditional RUN_DEPENDS on devel/py-ipaddr, depending on Python version.

While I'm here:

• Sort and group USE{S} entries
• Match COMMENT to setup.py:description
• Add test and post-extract targets, TEST_DEPENDS, and patch files so that tests can be run properly
• Pet several portlint warnings

[1] https://svnweb.freebsd.org/changeset/ports/404778
[2] https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=206645
[3] https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=206643

QA:

• portlint: OK (WARN: Makefile: [47]: possible use of "${CHMOD}")
• porttest: OK (poudriere: 11amd64, python27, python34)
• unittest: OK (Ran 425 tests in 0.155s)

PR: 206643
Reported by: danger
Approved by: portmgr (blanket)
Differential Revision: D5082

Approved by: ports-secteam (feld)