parse_config_line_from_str_verbose() already looks for strings
that are surrounded by quotes, and processes them with
unescape_string(). So things were getting decoded twice, which was
(in turn) playing havoc with backslashes on Windows.
config_get_lines is now split into two functions:
- config_get_lines which is the same as before we had %include
- config_get_lines_include which actually processes %include
