bump(app-crypt/gnupg): sync with upstream

The libusb updates are for use with USE=smartcard, so I can play with
using CoreOS as an offline gpg key management tool.

Packages updated:
  app-crypt/gnupg
  dev-libs/libusb
  dev-libs/libusb-compat
  virtual/libudev
  virtual/libusb
  virtual/udev
Merge pull request #119 from marineam/gnupg

bump(app-crypt/gnupg): sync with upstream