[docs] [issue8913] Document that datetime.__format__ is datetime.strftime

Changes by Florent Xicluna <florent.xicluna@gmail.com>: ---------- type: -> behavior versions: +Python 3.3 -Python 2.6, Python 3.1 _______________________________________ Python tracker <report@bugs.python.org> <http://bugs.python.org/issue8913> _______________________________________