In many cases it is preferrable for ConfigParser to
maintain the order
in which its items were added.  This small change adds
a `customdict`
default argument to *ConfigParser's constructor to
allow users to
specify a custom dict.

A useful example is::

    from ConfigParser import ConfigParser
    ConfigParser(customdict=my_ordered_dict)

One such `my_ordered_dict` could be the ordered
dictionary "odict"
<http://www.voidspace.org.uk/python/odict.html>.

Ordered dictionaries have been a recent popular topic on
comp.lang.python, and there are a few possibilities for
implementation, so it seems best that ConfigParser just
offer a
default argument to support such customization.

I can submit a documentation patch if this idea is
accepted.