Tag build swift-DEVELOPMENT-SNAPSHOT-2016-12-13-a
Merge remote-tracking branch 'origin/swift-3.1-branch' into stable

* origin/swift-3.1-branch:
  [analyzer] Add dispatch_data_create as a special case in RetainCountChecker.
  [analyzer] Remove an unused enum value in RetainCountChecker.
  [analyzer] pr31226: Disable CastSizeChecker in C++ because it's not quite ready.