device filtering support

[Pete Batard]

>> Can your you translate from VID:PID to those GUID things in your
>> backend? Maybe query the registry or something?
>
> Not that I know of.

There again some clarification:
Not that I know of, unless you parse the devices in the registry 
yourself. But in that case, we might as well do this for the whole 
enumeration process and ditch the use of SetupAPI.

Regards,

/Pete