Webform Quantity with Amount

Some of my clients want to have a form where they register a number of people for an event, so my solution to doing this is to have an amount set in one field and let them enter a quantity. Below is a patch that adds a quantity to the list of usable fields. If a Quantity is included, it multiplies the Quantity by the Amount and then submits that amount to the payment gateway. You can of course add it to the module, otherwise I hope somebody finds it useful.