The site can use this callback routine to interactively prompt
    for passwords. The routine uses either the standard OpenVMS
    password prompt or a prompt provided by the caller in the second
    argument.

    The password is returned in one of the following locations,
    depending on the value of the password_number argument:

    Value of Password_
    Number Argument        Location

    0 or -1                LGI$A_ICR_PWD1
    1 or -2                LGI$A_ICR_PWD2
    -3                     buffer argument

                                   NOTE

       This routine will do overstriking, if necessary, to support
       echo local terminals. See the VSI OpenVMS Programming
       Concepts Manual for more information about echo terminals.