Provide a C implementation of configmix.config._split_filters. This is needed as precondition for implementation interpolate_variables in C also. Currently the speedup is not measurable but it does not hurt also. Also provide some unit-tests for _split_filters().

# -*- 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"