* linux-nat.c (enum sigchld_state): Delete.

	* linux-nat.c (enum sigchld_state): Delete.
	(linux_nat_async_events_state): Delete.
	(struct waitpid_result): Delete.
	(waitpid_queue): Delete.
	(queued_waitpid_1): Delete.
	(async_file_flush): New.
	(queued_waitpid, push_waitpid): Delete.
	(async_file_mark): New.
	(drain_queued_events): Delete.
	(my_waitpid): Remove locally queued events handling.
	(linux_test_for_tracefork): Upjust.
	(linux_child_follow_fork): Ditto.
	(sync_sigchld_action): Delete.
	(blocked_mask): Reinstate.
	(async_sigchld_action): Rename to...
	(sigchld_action): ... this.
	(block_child_signals): New.
	(restore_child_signals_mask): New.
	(lin_lwp_attach_lwp): Adjust.
	(linux_nat_create_inferior): Ditto.
	(linux_nat_attach): Also use lp->status in async mode.
	(get_pending_status): Don't use queued_waitpid.
	(linux_nat_detach): Don't drain locally queued events.
	(linux_nat_resume): Allow pending wait statuses stored lp->status
	in async mode.  If returning early due to a pending event,
	re-register the event source.
	(stop_wait_callback): Allow pending wait statuses stored
	lp->status in async mode.
	(pipe_to_local_event_queue, local_event_queue_to_pipe): Delete.
	(linux_nat_wait): Rename to ...
	(linux_nat_wait_1): ... this.  Allow pending wait statuses stored
	lp->status in async mode.  Always add WNOHANG to the waitpid
	options in async mode.
	(linux_nat_wait): New.
	(kill_callback): Don't drain locally queued events.
	(sigchld_handler): Rewrite.
	(linux_nat_is_async_p, linux_nat_can_async_p): Fix comments to
	refer to "set target-async".
	(linux_nat_async_mask): If in non-stop, and re-enabling async
	mode, re-register the target event source in the event loop.
	(linux_nat_event_pipe_pop, linux_nat_event_pipe_push)
	(get_pending_events, async_sigchld_handler)
	(linux_nat_async_events): Delete.
	(handle_target_event): New.
	(linux_nat_async_file_handler): Delete.
	(linux_async_pipe): New.
	(linux_nat_async): Only re-register in the event loop if not
	registered yet.  Always notify the event-loop once if enabling the
	event source.
	(linux_nat_stop_lwp): Rewrite to handle pending events stored in
	lp->status, not in the locally queued event list.
	(linux_nat_stop): Don't mask out async event handling.
	(linux_nat_setup_async): Delete.
	(_initialize_linux_nat): Adjust.
	(lin_thread_get_thread_signals): blocked_mask is global again.
	Adjust.