Fix an issue with forking and signal socketpairs in select/poll backends

Nicholas Marriott identifies an issue where a signal socketpair
doesn't get recreated if the event backend doesn't set event_reinit.

event.c

@@ -279,9 +279,14 @@ event_reinit(struct event_base *base)
 	int res = 0;
 	struct event *ev;
 
+#if 0
+	/* Right now, reinit always takes effect, since even if the
+	   backend doesn't require it, the signal socketpair code does.
+	 */
 	/* check if this event mechanism requires reinit */
 	if (!evsel->need_reinit)
 		return (0);
+#endif
 
 	/* prevent internal delete */
 	if (base->sig.ev_signal_added) {