Re-branch swift-4.0-branch '2a4c30f4ff2f5f39bace5b05e7d87b4c526e53a7' from master 'db6f71e32ac2e101846a147f7b00db88d4ac11d1'

Merge commit '2a4c30f4ff2f5f39bace5b05e7d87b4c526e53a7' into swift-4.0-branch