Google Checkout for Oscommerce 1.0

This contribution will add a full support of a Google Checkout service to your Oscommerce store.
While using Google checkout at your OsCommerce store you will be able to allow your customers to buy from you quickly and securely, using a single username and password without any account creation.
Benefits:
Google Checkout for OsCommerce will run on any PHP4 or PHP5 enabled web-server
No requirements for using libXML and libCURL installed.
Full google checkout sandbox support
Full shipping support using merchant-calculations google checkout shipping
Full tax support over merchant-calculations in google checkout using taxes from OsCommerce
Basic shipping modules like flat-rate and per-item shipping supported
Basic USA shipping modules: UPS, USPS, FEDEX with real-time quotes are supported
Order management inside OsCommerce Administration area: orders placed via Google Checkout will appear in your OsCommerce admin, and you will be able to process them (Charge, Refund, Ship, Track etc) from your usual OsCommerce orders page