Facebook iOS SDK 3.11.1

Summary:
    see https://developers.facebook.com/ios/change-log-3.x/

Upgrading:
    https://developers.facebook.com/docs/ios/upgrading/

Reviewed By: jacl

Test Plan: Release Testing.
Merge commit '283b0d0dd5cde6fd6abef87c028df93bc11fe5df'