title: UIViewController reported as responding to addChildViewController: on iOS 4
body: <p>Has anyone else encountered this? The following code reports "YES" when running on the iOS 4 simulator but according to the Apple docs the method addChildViewController is only available on iOS 5 and later. This doesn't seem like the correct behavior, is this a bug?</p>
  
  <pre><code>if([UIViewController instancesRespondToSelector:@selector(addChildViewController:)]) {
      NSLog(@"YES"); 
  } else {
      NSLog(@"NO");
  }
  </code></pre>