Attribute values are not urlencoded and therefore an ampersand will break functionality

I have a simple attribute that allows the user to enter text into a text field. When the user clicks the Add to Cart button, the user's text is added as a query string variable by the uc_node_checkout_add_to_cart_submit function.

The uc_node_checkout_add_to_cart_submit does not urlencode the submitted value so any text that contains a & is cut short and subsequent attributes break.

Solution: urlencode the oid variable. I added the urlencode step to the code and rolled that attached patch. I'm not sure if I picked the best place to do so, but it seemed to work.