Facebook iOS SDK 3.10

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

Upgrading from 3.9
     https://developers.facebook.com/docs/ios/upgrading-from-3.9-to-3.10/

Reviewed By: jacl

Test Plan: Release Testing.
Merge 3.10 Facebook SDK branch 'upstream/master'