Notification: fix addObserver(forName:object:queue:using:) signature

Author: ianpartridge

Foundation/NSNotification.swift

@@ -187,8 +187,13 @@ open class NotificationCenter: NSObject {
             self._observers = _observers.filterOutObserver(observer, name: aName, object: object)
         })
     }
-    
+
+    @available(swift, obsoleted: 4.0)
     open func addObserver(forName name: Notification.Name?, object obj: Any?, queue: OperationQueue?, usingBlock block: @escaping (Notification) -> Void) -> NSObjectProtocol {
+        return addObserver(forName: name, object: obj, queue: queue, using: block)
+    }
+
+    open func addObserver(forName name: Notification.Name?, object obj: Any?, queue: OperationQueue?, using block: @escaping (Notification) -> Void) -> NSObjectProtocol {
         let object = NSObject()
 
         let newObserver = NSNotificationReceiver()