Implement option parsing with getopt_long.
Implement option parsing with getopt_long.

Done in anticipation of the various options that might be interesting
to set with Validation protocol 2.0.

kellyjf/yubi,kellyjf/yubi,Yubico/yubico-c-client,Yubico/yubico-c-client,Yubico/yubico-c-client