Fix C-g handling with multiple ttys.

Fix C-g handling with multiple ttys.

src/sysdep.c (init_sys_modes): Disable interrupt and quit keys on
secondary terminals.  Added a big fat comment about this.

lib-src/emacsclient.c (init_signals): Don't pass SIGINT and SIGQUIT to Emacs.

src/keyboard.c (interrupt_signal): Exit Emacs if there are no frames
on the controlling tty.  Otherwise set internal_last_event_frame to
the controlling tty's top frame.

src/term.c (ring_bell, tty_ring_bell): Don't look at updating_frame.

git-archimport-id: lorentey@elte.hu--2004/emacs--multi-tty--0--patch-52