Add support for UnsafeRawBufferPointer to DispatchData
Add support for UnsafeRawBufferPointer to DispatchData

(Radar 30699743)

apple/swift-corelibs-libdispatch,apple/swift-corelibs-libdispatch,apple/swift-corelibs-libdispatch,apple/swift-corelibs-libdispatch