Allow setting timestamp in gzip-compressed tarfiles

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2017-09-20.05:11:11.655>
labels = ['3.7', 'type-feature', 'library']
title = 'Allow setting timestamp in gzip-compressed tarfiles'
updated_at = <Date 2021-05-04.00:32:57.741>
user = 'https://github.com/randombit'

bugs.python.org fields:

activity = <Date 2021-05-04.00:32:57.741>
actor = 'FFY00'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2017-09-20.05:11:11.655>
creator = 'randombit'
dependencies = []
files = []
hgrepos = []
issue_num = 31526
keywords = []
message_count = 5.0
messages = ['302590', '305915', '306065', '375849', '375850']
nosy_count = 5.0
nosy_names = ['jonash', 'martin.panter', 'randombit', 'maarten', 'FFY00']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue31526'
versions = ['Python 3.7']