* dbus/dbus-errors.c: (dbus_set_error):
	* dbus/dbus-errors.h:
	Add a few errors and make dbus_set_error void.

	* dbus/dbus-sysdeps.c:
	(_dbus_errno_to_string), (close_and_invalidate), (make_pipe),
	(write_err_and_exit), (read_ints), (do_exec), (_dbus_spawn_async):
	* dbus/dbus-sysdeps.h:
	Add _dbus_spawn_async.

	* test/spawn-test.c: (main):
	Test for _dbus_spawn_async.