title: google admob undefined symbol for architecture armv7
body: <p>i have replaced older version of admob 6.6.1  with latest admob library  version 6.12.0 but i get this error although every thing is fine. I am using xcode 6.0.1, how to resolve this issue, any help?</p>
  
  <pre><code>Undefined symbols for architecture armv7:
    "_OBJC_CLASS_$_EKEvent", referenced from:
        objc-class-ref in libGoogleAdMobAds.a(GADOpener.o)
    "_OBJC_CLASS_$_EKEventEditViewController", referenced from:
        objc-class-ref in libGoogleAdMobAds.a(GADOpener.o)
  ld: symbol(s) not found for architecture armv7
  clang: error: linker command failed with exit code 1 (use -v to see invocation)
  </code></pre>