lang/python: Update to 2.7.11

Announcement: https://www.python.org/downloads/release/python-2711/
Mailing list: https://mail.python.org/pipermail/python-announce-list/2015-December/010999.html
Changelog: https://hg.python.org/cpython/raw-file/v2.7.11/Misc/NEWS

Important changes for this release:

• Python 2.7.11 is a bug fix release of the Python 2.7.x series.

Reviewed by: koobs
Sponsored by: EMC / Isilon Storage Division
Differential Revision: https://reviews.freebsd.org/D4413