Index of changes:
变动索引：
1. hook_calculate_tax() was added
2. 添加了hook_calculate_tax()
hook_calculate_tax() was added
添加了hook_calculate_tax()
This hook allows Ubercart to use multiple tax calculation schemes on its orders. The only argument is the entire order object for which the taxes will be calculated.
这个钩子让Ubercart可以对它的订单使用多个税收计算方案。这里面仅有的一个参数就是，所要计算的订单对象/
The hook implementations should return an array of tax line items, which are arrays with the following keys:
钩子函数应该返回一个数组，里面包含了税收行项（line items），里面用到以下键：
· id
· name
· amount
· weight (optional)
Make sure that your module's tax ids are properly namespaced to prevent collisions with other taxes.
确保你模块的税收ids使用了合适的命名空间，以避免与其它的税收冲突。
相关链接： Think in Drupal
http://www.ubercart.org/docs/developer/6867/api_changes_ubercart_13_14
