bug#1794: accessibility vs. password echoing

[jidanni]

Try this: turn out the room lights so you can't see the keyboard, but
only the screen. Now try to type a password in M-x shell
$ echo -e 'password: '; read p; echo $p
Did you get back what you thought you typed in?
Anyway, without an option to echo back what you typed, perhaps some
disabled users will be at a disadvantage.