Merge remote-tracking branch 'origin/swift-4.0-branch' into stable

* origin/swift-4.0-branch:
  [LaxConversions] Revert lax vector changes causing regressions
  Merging r292991: ------------------------------------------------------------------------ r292991 | rsmith | 2017-01-24 15:18:28 -0800 (Tue, 24 Jan 2017) | 3 lines