vendor: pull in support for USB devices via libusb/gousb

vendor.conf

vendor/github.com/karalabe/gousb/.gitignore

vendor/github.com/karalabe/gousb/.travis.yml

vendor/github.com/karalabe/gousb/LICENSE

vendor/github.com/karalabe/gousb/README.md

vendor/github.com/karalabe/gousb/appveyor.yml

vendor/github.com/karalabe/gousb/internal/libusb/AUTHORS

vendor/github.com/karalabe/gousb/internal/libusb/COPYING

...github.com/karalabe/gousb/internal/libusb/libusb/config.h

...r/github.com/karalabe/gousb/internal/libusb/libusb/core.c

...ub.com/karalabe/gousb/internal/libusb/libusb/descriptor.c

...ithub.com/karalabe/gousb/internal/libusb/libusb/hotplug.c

...ithub.com/karalabe/gousb/internal/libusb/libusb/hotplug.h

vendor/github.com/karalabe/gousb/internal/libusb/libusb/io.c

...github.com/karalabe/gousb/internal/libusb/libusb/libusb.h

...ithub.com/karalabe/gousb/internal/libusb/libusb/libusbi.h

...com/karalabe/gousb/internal/libusb/libusb/os/darwin_usb.c

...com/karalabe/gousb/internal/libusb/libusb/os/darwin_usb.h

...karalabe/gousb/internal/libusb/libusb/os/haiku_pollfs.cpp

....com/karalabe/gousb/internal/libusb/libusb/os/haiku_usb.h