event/InotifyEvent: add method IsDefined()

src/event/InotifyEvent.hxx

@@ -51,6 +51,13 @@ public:
 		return event.GetEventLoop();
 	}
 
+	/**
+	 * Is the inotify file descriptor still open?
+	 */
+	bool IsDefined() const noexcept {
+		return event.IsDefined();
+	}
+
 	/**
 	 * Re-enable polling the inotify file descriptor after it was
 	 * disabled by Disable().