Support replacing global function pointers in a shared library

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2020-07-20.15:21:21.724>
labels = ['ctypes', 'type-bug']
title = 'Support replacing global function pointers in a shared library'
updated_at = <Date 2020-07-20.15:21:21.724>
user = 'https://bugs.python.org/UnaiMartinez'

bugs.python.org fields:

activity = <Date 2020-07-20.15:21:21.724>
actor = 'Unai Martinez'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['ctypes']
creation = <Date 2020-07-20.15:21:21.724>
creator = 'Unai Martinez'
dependencies = []
files = []
hgrepos = []
issue_num = 41348
keywords = []
message_count = 1.0
messages = ['374013']
nosy_count = 1.0
nosy_names = ['Unai Martinez']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue41348'
versions = []