* fhandler.h (fhandler_termios::line_edit): Change return from an int to an

* fhandler.h (fhandler_termios::line_edit): Change return from an int to an
enum to allow the function to return an error.
* fhandler_console.cc (fhandler_console::read): Update the line_edit call to
use the new enum.
* fhandler_termios.cc (fhandler_termios::line_edit): Change return from an int
to an enum to allow the function to return an error.  Put put_readahead call
before doecho for future patch.
* fhandler_tty.cc (fhandler_pty_master::write): Change to call line_edit one
character at a time, and stop if an error occurs.