Coding standard changes
Coding style cleanup for cart api, no intentional logic changes
Updated headers, documentation and confirmed return values
Merge remote-tracking branch 'upstream/master' into cart_class_cart_api_cleanup

Conflicts:
	wpsc-includes/cart.class.php
Merge pull request #998 from JeffPyeBrook/cart_class_cart_api_cleanup

Updates to protect cart template API and WPEC from improper usage