Tag build swift-DEVELOPMENT-SNAPSHOT-2017-02-15-a
Merge remote-tracking branch 'origin/swift-4.0-branch' into stable

* origin/swift-4.0-branch:
  Merging r294527: ------------------------------------------------------------------------ r294527 | arnolds | 2017-02-08 14:30:47 -0800 (Wed, 08 Feb 2017) | 14 lines
  Merging r294551: ------------------------------------------------------------------------ r294551 | arnolds | 2017-02-08 17:52:17 -0800 (Wed, 08 Feb 2017) | 10 lines
  ReleaseNotes: coroutines; by Gor Nishanov
  ReleaseNotes: llvm-cov blurb; by Vedant Kumar