Tag build swift-DEVELOPMENT-SNAPSHOT-2016-06-20-a
Merge remote-tracking branch 'origin/swift-3.0-branch' into stable

* origin/swift-3.0-branch:
  {x86_64,i386,x86_64h}-apple-macosx should also be XFAILED when 'darwin' is XFAILED.
  [lit] Refactor lit detection of macOS triples to use a centralized query in lit.util.isMacOSTriple.