Fix EV_CLOSED detection/reporting (epoll only)

- EV_CLOSED is EPOLLRDHUP in epoll
- EPOLLRDHUP reported w/o EPOLLHUP if the socket closed with shutdown(SHUT_WR)
- EPOLLRDHUP reported w/  EPOLLHUP if the socket closed with close()
  so in this case epoll backend will detect this event as error
  (EV_READ|EV_WRITE), since the epoll_ctl() will return EPOLLRDHUP with
  EPOLLHUP set, but this is not correct, let's fix this.

Fixes: libevent#984

epoll.c

@@ -487,7 +487,9 @@ epoll_dispatch(struct event_base *base, struct timeval *tv)
 			continue;
 #endif
 
-		if (what & (EPOLLHUP|EPOLLERR)) {
+		if (what & EPOLLERR) {
+			ev = EV_READ | EV_WRITE;
+		} else if ((what & EPOLLHUP) && !(what & EPOLLRDHUP)) {
 			ev = EV_READ | EV_WRITE;
 		} else {
 			if (what & EPOLLIN)

test/regress.c

@@ -512,13 +512,8 @@ test_simpleclose(void *ptr)
 		tt_assert(!event_base_loopexit(base, &tv));
 	}
 
-	/* via close() */
-	if (pair[1] == -1) {
-		tt_int_op(event_base_loop(base, EVLOOP_NONBLOCK), ==, 0);
-	} else {
-		tt_int_op(event_base_loop(base, EVLOOP_NONBLOCK), ==, !persist);
-		tt_int_op(got_event, ==, (events & ~EV_PERSIST));
-	}
+	tt_int_op(event_base_loop(base, EVLOOP_NONBLOCK), ==, !persist);
+	tt_int_op(got_event, ==, (events & ~EV_PERSIST));
 
 end:
 	if (ev)