[swift-build-dev] Merged master into swift-3.1-branch

[mishal_shah]

I just merged master into swift-3.1-branch for following projects. 

https://github.com/apple/swift
https://github.com/apple/swift-lldb
https://github.com/apple/swift-corelibs-foundation
https://github.com/apple/swift-corelibs-libdispatch
https://github.com/apple/swift-corelibs-xctest
https://github.com/apple/swift-integration-tests
https://github.com/apple/swift-xcode-playground-support
https://github.com/apple/swift-package-manager
https://github.com/apple/swift-llbuild

Thanks, 
Mishal Shah