Attached are patches for 1.7rc1 and 1.6.3 that add support for USB quirks files to the libusb-based USB backend.  The purpose of these patches is to allow third-party drivers (Gutenprint, others) that provide their own backends to blacklist the USB printers they support, or for those drivers to identify the specific quirks those printers need to work with the standard USB backend.

If there are no objections these will be part of the 1.6.4 update (last in that series) and part of the 1.7.0 release.