Update Security String to 2016-04-02 in preparation for April 2016 Security OTA v2 - kernel updates with patches for CVE-2015-1805 am: 2b71be5 am: df28b90 am: b90d094 am: fa24625 am: d7bf980
am: 87582a8

* commit '87582a8758970cc1178c9c63a7e5f8d97b02aa5d':
  Update Security String to 2016-04-02 in preparation for April 2016 Security OTA v2 - kernel updates with patches for CVE-2015-1805