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().

[config]
tmpdir = {{_tmpdir}}\2

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

[config.db.locinfo.ro]
hostname = 3rd-host
hostname2 = {{db.locinfo.ro.hostname}}{{db.locinfo.ro.hostname}}