Restore stealth legacy login prompt (NN:)
This old prompt used to be sent for any login scripts (e.g. QWKnet via dial-up) that would key off that WWIV-like "name or number" (NN:) prompt, but was removed (accidentally?) in commit fedabb0b. Send "NN: " and "PW: " (include the trailing space, just in case), and use carriage return to move back (and overwrite) rather than 4 backspaces.