kqueue_register
error = kqueue_register(kq, kevp, 0, p);
error = kqueue_register(kq, &kev, 0, NULL);
error = kqueue_register(p->p_kq, kevp, pollid, p);
error = kqueue_register(p->p_kq, &kev, 0, p);
extern int kqueue_register(struct kqueue *kq, struct kevent *kev,