dir(<bound method>) should include dunder attributes of the unbound method

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2016-12-30.21:51:10.086>
labels = ['interpreter-core', 'type-bug', '3.7']
title = 'dir(<bound method>) should include dunder attributes of the unbound method'
updated_at = <Date 2017-01-06.21:51:15.327>
user = 'https://github.com/anntzer'

bugs.python.org fields:

activity = <Date 2017-01-06.21:51:15.327>
actor = 'terry.reedy'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Interpreter Core']
creation = <Date 2016-12-30.21:51:10.086>
creator = 'Antony.Lee'
dependencies = []
files = []
hgrepos = []
issue_num = 29117
keywords = []
message_count = 2.0
messages = ['284347', '284859']
nosy_count = 3.0
nosy_names = ['terry.reedy', 'Antony.Lee', 'xiang.zhang']
pr_nums = []
priority = 'normal'
resolution = None
stage = 'test needed'
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue29117'
versions = ['Python 3.6', 'Python 3.7']