(Qtimer_event): New symbol.

(Qtimer_event): New symbol.
(read_char, kbd_buffer_get_event): Don't sleep past the next timer.
(readable_events, kbd_buffer_get_event): Check for timer events.
(make_lispy_event): Handle timer events.
(timer_check): New function.
(Vtimer_list): New variable.
(syms_of_keyboard): Set up Qtimer_event and Vtimer_list.