Improve zipfile: add support for symlinks

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2019-08-22.21:14:36.379>
labels = ['type-feature', 'library', '3.9']
title = 'Improve zipfile: add support for symlinks'
updated_at = <Date 2021-09-25.17:47:38.187>
user = 'https://github.com/zaphodef'

bugs.python.org fields:

activity = <Date 2021-09-25.17:47:38.187>
actor = 'serhiy.storchaka'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2019-08-22.21:14:36.379>
creator = 'zaphodef'
dependencies = []
files = []
hgrepos = []
issue_num = 37921
keywords = ['patch']
message_count = 4.0
messages = ['350231', '352932', '362217', '402638']
nosy_count = 3.0
nosy_names = ['serhiy.storchaka', 'Henning.von.Bargen', 'zaphodef']
pr_nums = ['15401']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue37921'
versions = ['Python 3.9']