(the_only_perd): Define this var here.

(the_only_perd): Define this var here.
(kbd_buffer, kbd_fetch_ptr, kbd_store_ptr): Delete; now part of perd.
(find_active_event_queue): New function.
(readable_events, kbd_buffer_get_event, swallow_events): Use it.
(kbd_buffer_store_event): Store in EVENT's frame's queue.
(Fdiscard_input, stuff_buffered_input): Use perd.
(init_keyboard): Initialize the new vars.
kbd_buffer is now a pointer, not an array.