Discounts are not applied when using paypal and order is itemized

Issue Summary

When checking out through paypal, and if the paypal option "Submit an itemized order showing each product and description." is selected, the discount applied to the order is not passed on to paypal. This has the effect of not applying the discount at all. The workaround is to use the "Submit the whole order as a single line item" paypal setting. (admin/store/settings/payment/edit/methods) But it would be nice if the discount could be passed on to paypal in an itemized order.