device filtering support

[Segher Boessenkool]

> I also don't have much of a problem with Segher's suggestion of having
> additonal API calls for filtered, though I think the filters Travis
> would like to apply would be Windows specific GUIDs related to devices
> and drivers rather than general USB items such as VID:PID.

Can your you translate from VID:PID to those GUID things in your
backend?  Maybe query the registry or something?

If not, there is no generic interface that would work for you it
seems.


Segher