* keyboard.c (pending_signals): New var.

* keyboard.c (pending_signals): New var.
(poll_for_input, input_available_signal, init_keyboard): Set it.
(process_pending_signals): New function.

* lisp.h (QUIT): Check pending_signals instead of
interrupt_input_pending.  Use process_pending_signals.

* atimer.c (run_timers, alarm_signal_handler): Update
pending_signals.

* process.c (wait_reading_process_output): Use
process_pending_signals.

* sysdep.c (emacs_write): Use process_pending_signals.

* xterm.c (XTread_socket): Update pending_signals.

* w32term.c (w32_read_socket): Update pending_signals.

* w32inevt.c (w32_console_read_socket): Update pending_signals.

* blockinput.h: Add declaration for pending_signals.