Mozilla: Add-on update site certificate pin expiration (MFSA 2016-85, MFSA 2016-86)

Mozilla Firefox before 49.0, Firefox ESR 45.x before 45.4, and Thunderbird 45.4 rely on unintended expiration dates for Preloaded Public Key Pinning, which allows man-in-the-middle attackers to spoof add-on updates by leveraging possession of an X.509 server certificate for addons.mozilla.org...