Clean up redundant and orphaned constants for TEXT_CLOSE_WINDOW
ref: http://www.zen-cart.com/showthread.php?212344-TEXT_CLOSE_WINDOW-in-info_shopping_cart-php-of-No-Effect
Fixes #78 - Remove Attributes Preview Incomplete
Merge pull request #83 from drbyte/v160

Clean up redundant and orphaned constants for TEXT_CLOSE_WINDOW
Merge pull request #84 from drbyte/attr-preview-cleanup

Fixes #78 - Remove Attributes Preview Incomplete