Check for Mac OS X 10.4 kqueue bug properly

EV_ERROR is a bit in struct kevent::flags. Other bits may be set too.

Actually we have osx builds on travis-ci, but it uses osx 10.9.5, and we don't
have warnings there, since I guess that there is no OR'ing with previous flag
in case of error, while in 10.12 there is OR.

Fixes: libevent#377
Fixes: libevent#376
Link: https://crbug.com/626534
Link: https://travis-ci.org/libevent/libevent/jobs/141033429

kqueue.c

@@ -154,7 +154,7 @@ kq_init(struct event_base *base)
 	if (kevent(kq,
 		kqueueop->changes, 1, kqueueop->events, NEVENT, NULL) != 1 ||
 	    (int)kqueueop->events[0].ident != -1 ||
-	    kqueueop->events[0].flags != EV_ERROR) {
+	    !(kqueueop->events[0].flags & EV_ERROR)) {
 		event_warn("%s: detected broken kqueue; not using.", __func__);
 		goto err;
 	}