title: Wierd error when trying to run app with AdMob
body: <pre><code>    Undefined symbols for architecture i386:
    "_AudioServicesPlaySystemSound", referenced from:
        -[GADWebViewDelegate webView:shouldStartLoadWithRequest:navigationType:] in libGoogleAdMobAds.a(GADWebViewDelegate.o)
    "_OBJC_CLASS_$_MFMailComposeViewController", referenced from:
        objc-class-ref in libGoogleAdMobAds.a(GADOpener.o)
    "_OBJC_CLASS_$_MFMessageComposeViewController", referenced from:
        objc-class-ref in libGoogleAdMobAds.a(GADOpener.o)
  ld: symbol(s) not found for architecture i386
   clang: error: linker command failed with exit code 1 (use -v to see invocation)
  </code></pre>
  
  <p>What does it means? what do I need to do in order to fix that?</p>
  
  <p>Thanks alot.</p>