title: Use of undeclared identifier: ASIdentifierManager
body: <p>I am using the following code to show the unique identifier to be used for admob test apps. </p>
  
  <p>This is with my applicationDidFinishLaunching...</p>
  
  <pre><code>// Print IDFA (from AdSupport Framework) for iOS 6 and UDID for iOS &lt; 6.
  if (NSClassFromString(@"ASIdentifierManager")) {
      NSLog(@"GoogleAdMobAdsSDK ID for testing: %@" ,
            [[[ASIdentifierManager sharedManager] advertisingIdentifier] UUIDString]);
  } else {
      NSLog(@"GoogleAdMobAdsSDK ID for testing: %@" ,
            [[UIDevice currentDevice] uniqueIdentifier]);
  }
  </code></pre>
  
  <p>I get an error when building 'Use of undeclared identifier: ASIdentifierManager'</p>
  
  <p>I have the AdSupport framework linked and can access the files the identifier manager is declared in, but it still doesn't recognise that?</p>
  
  <p>I have cleaned build folder, restarted xCode same result.</p>