Make `--batch-mode' without `--interactive' imply non-interactive.

Make `--batch-mode' without `--interactive' imply non-interactive.

In this case, don't check whether stdin/stdout/stderr are ttys to
determine whether we are interactive.

This keeps `scheme --batch-mode' from futzing with the tty interrupt
characters, so that if you run it from a script, there is no window
during which ^G becomes the terminal's interrupt character and ^C its
quit character.  E.g., if you have set `stty intr ^C', then Scheme
won't interfere with that while you run your script.