(opts): Add -d option.
(GetPW): Add server parameter which is given to Net functions.
(ChangePW): Ditto.
(PrintPW): Ditto.
(SetModals): Ditto.
(usage): Add description for -d/--logonserver option.
(main): Add option handling for -d/--logonserver. Use LOGONSERVER
environment variable content for server to contact, unless
-d/--logonserver option is given. If both is missing, use NULL.