darwin-nat.c: handle Darwin 16 (aka Sierra).

darwin-nat.c: handle Darwin 16 (aka Sierra).

Support message from new task and dead name notification on task of an
existing process.
With Sierra, exec(2) terminate the current task and creates a new one.
'set startup-with-shell off' must still be used on Darwin 16.

2016-11-09  Tristan Gingold  <gingold@adacore.com>

	* darwin-nat.c (find_inferior_task_it): Fix indentation.
	(find_inferior_notify_it): Remove.
	(find_inferior_pid_it): New function.
	(darwin_find_inferior_by_notify): Remove.
	(darwin_find_inferior_by_pid): New function.
	(darwin_find_new_inferior): New function.
	(darwin_check_message_ndr): New function from
	darwin_decode_exception_message.
	(darwin_decode_exception_message): Call darwin_check_message_ndr.
	Handle SIGTRAP addressed to an unknown task (when a task spawned).
	(darwin_decode_notify_message): New function.
	(darwin_decode_message): Handle unknown task.
	(darwin_deallocate_threads): New function from darwin_mourn_inferior.
	(darwin_mourn_inferior): Use darwin_deallocate_threads and
	darwin_deallocate_exception_ports.
	(darwin_deallocate_exception_ports): New function from
	darwin_mourn_inferior.
	(darwin_setup_exceptions): New function from darwin_attach_pid.
	(darwin_setup_request_notification): Likewise.
	(darwin_attach_pid): Call darwin_setup_request_notification and
	darwin_setup_request_notification.