Foundation overlay: add String.stringByApplyingTransform()
Foundation overlay: add String.stringByApplyingTransform()

This API is new in OS X 10.11 and iOS 9.0.

rdar://20645458

Swift SVN r28315

apple/swift-corelibs-foundation,apple/swift-corelibs-foundation,apple/swift-corelibs-foundation,apple/swift-corelibs-foundation,apple/swift-corelibs-foundation