Detect Tiger kqueue bug properly on Sierra and later
https://github.com/libevent/libevent/issues/376
https://github.com/libevent/libevent/commit/df6f99e5b51a3c0786f54cb9822604ec63385400
--- kqueue.c.orig	2015-01-05 08:34:32.000000000 -0600
+++ kqueue.c	2016-09-12 14:24:08.000000000 -0500
@@ -153,7 +153,7 @@
 	if (kevent(kq,
 		kqueueop->changes, 1, kqueueop->events, NEVENT, NULL) != 1 ||
 	    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__);
 		free(kqueueop->changes);
 		free(kqueueop->events);
