5 digit postal codes

[perlDreamer]

According to this Wikipedia page:

http://en.wikipedia.org/wiki/List_of_postal_codes

There are at least 10 other countries that use 5 digit postal codes, including France, Italy, Costa Rica and Mexico.

USPS::RateRequest needs to accept a 2 character postal code and use that instead of the postal code to determine whether an outgoing request is domestic or international.