Improve detection of The Imaging Source Cameras that implement the UVC protocols but don't announce themselves as UVC cameras (and ignore similar cameras that appear to be UVC but are not).
Improve detection of The Imaging Source Cameras that implement
the UVC protocols but don't announce themselves as UVC cameras
(and ignore similar cameras that appear to be UVC but are not).

Also tidy up an unused variable assignment when compiling
without debugging.

ktossell/libuvc,ktossell/libuvc