/**	@file	dk3echo.h	Keyboard echo control.

This module can be used to disable keyboard echo temporarily, i.e. to
enter a password.

@code
dk3_echo_t	echodata;
if(dk3sf_echo_test_tty()) {
  if(dk3sf_echo_save(&echodata)) {
    if(dk3sf_echo_off(&echodata)) {
      ... success, keyboard echo is disabled, now read password ...
    } else {
      ... error, failed to disable keyboard echo ...
    }
    dk3sf_echo_restore(&echodata);
  } else {
    ... error, failed to save current settings ...
  }
} else {
  ... error, standard input is not a terminal ...
}
@endcode
*/