(timers_run): New variable, incremented when a timer is

(timers_run): New variable, incremented when a timer is
run directly.
(timer_check, swallow_events): Increment timers_run.
(swallow_events): Redisplay if get_input_pending has run timers.
(detect_input_pending_run_timers): New arg DO_DISPLAY.

(init_keyboard): Initialize timer_idleness_start_time.

(reinvoke_input_signal): Use getpid.

(input_poll_signal): Use start_polling
after first incrementing poll_suppress_count.