setup.py: Check DLL version when packaging

This has two benefits:
- this should help detect issues like how python-libusb1 bundled libusb
  1.0.25 instead of the intended 1.0.26 as documented (traces are now gone,
  but I suspect a libusb release mixup as the SHA256 does not match the
  now-available 1.0.26 release 7z)
- it makes it easier to check what version was packaged, instead of having
  to check which 7z matches the bundled sha256