Unexpected dependency on libusb.dll

[cmaglie]

arduino/Arduino#5173
arduino/Arduino#5173 (comment)

Found it at last, avrdude-6.3-arduino2 had an unwanted dependency on libusb-0.dll . Launching the IDE by clicking the .ino bypasses the inclusion of IDE root in PATH, so the dll doesn't get loaded at runtime. Since that release of avrdude was quite unlucky we should revert to 6.0.1 in upcoming release, so this problem will be solved (and we must keep in mind to check for it before the next release).