Add an optional C-implementation for configmix.config.unquote and configmix.config.pathstr2path. This is currently for Python 3.5+. It is tested with Python 3.7 and Python3.8 (FreeBSD 12.2 amd64, LLVM 10.0.1). A build for the stable API ("abi3") fails because PyUnicode_New() is currently not in the stable API. Also includes are extended tests for unquote() and pathstr2path().

# -*- coding: utf-8 -*-

tmpdir = '{{_tmpdir}}\4'

[db.user]
name = "the_database_user_2"
__doc2 = "Overwriting a comment"
pwd="the-database-password-2"

[db.locinfo.ro]
hostname = "3rd-host"