Initial import of gone.

Initial import of gone.

Gone is a utility that locks a terminal  with  a  password
chosen by the user.  Gone will prompt the user for a password
(unless the -p option is given, then gone will use the system
password), then print the gone banner, then drop into the gone
shell.  From this shell, only a restricted set of commands
can be run.  Gone will also disallow messages by  removing
permissions  on  the parent tty.  After the timeout period
(10 minutes by default), gone will automatically log the user out.