add support for USB_GET_DEVICEINFO and USB_GET_STRING_DESC ioctls,
with same meaning as for ugen(4)

Yes, some devices return incorrect lengths in their string
descriptors.  Rather than losing, do what Windows does: just
request the maximum size, and allow a shorter response.  Obsoletes
the need for UQ_NO_STRINGS, and therefore these "quirks" are removed.

In the "seemed like a good idea until I found the fatal flaw"
department...  Attempting to read a maximum-size string descriptor
causes my kue device to go completely apeshit.  So, go back to the
original method, but allow the device to return a shorter string than
it claimed.