Nettle.BlockCipher16: Added new AEAD mode: EAX. Test vectors from the EAX specification. FIXME: Nettle only supports EAX with block ciphers having a 16 byte block size. The actual specification supports any block size. Consider implementing a generic version as well. FIXME: Nettle also has an AES-specific implementation of EAX. Consider adding support for it too.