Use of argument clinic like parsing and `METH_FASTCALL` support in extension modules

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2020-01-15.21:03:38.635>
labels = ['type-feature', 'expert-argument-clinic']
title = 'Use of argument clinic like parsing and `METH_FASTCALL` support in extension modules'
updated_at = <Date 2020-01-15.21:03:38.635>
user = 'https://github.com/seberg'

bugs.python.org fields:

activity = <Date 2020-01-15.21:03:38.635>
actor = 'seberg'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Argument Clinic']
creation = <Date 2020-01-15.21:03:38.635>
creator = 'seberg'
dependencies = []
files = []
hgrepos = []
issue_num = 39347
keywords = []
message_count = 1.0
messages = ['360073']
nosy_count = 2.0
nosy_names = ['larry', 'seberg']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue39347'
versions = []