devel/py-python-pcre: add port.

A Python PCRE library

WWW: https://github.com/awahlig/python-pcre

PR: 196947
Differential Revision: https://reviews.freebsd.org/D1596
Submitted by: Maxim Filimonov <che@bein.link>
Reviewed by: koobs, swills (while still in mentorship)