swift

26716520 - [BitwiseCopyable] Avoid a condfail.

[BitwiseCopyable] Avoid a condfail. The standard library defines ``` protocol BitwiseCopyable {} typealias _BitwiseCopyable = BitwiseCopyable ``` For current compilers, `BitwiseCopyable` is a "known protocol". For older compilers, it is not; instead `_BitwiseCopyable` is. So print the following into the swiftinterface for those older compilers: ``` protocol _BitwiseCopyable {} typealias BitwiseCopyable = _BitwiseCopyable ``` rdar://127755503