Introduce a method to concatenate regex patterns

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2018-05-27.08:53:27.253>
labels = ['expert-regex', 'type-feature', '3.7']
title = 'Introduce a method to concatenate regex patterns'
updated_at = <Date 2018-05-28.08:16:03.689>
user = 'https://bugs.python.org/aleskva'

bugs.python.org fields:

activity = <Date 2018-05-28.08:16:03.689>
actor = 'serhiy.storchaka'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Regular Expressions']
creation = <Date 2018-05-27.08:53:27.253>
creator = 'aleskva'
dependencies = []
files = []
hgrepos = []
issue_num = 33658
keywords = []
message_count = 2.0
messages = ['317787', '317829']
nosy_count = 5.0
nosy_names = ['ezio.melotti', 'mrabarnett', 'THRlWiTi', 'serhiy.storchaka', 'aleskva']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue33658'
versions = ['Python 3.7']