[gardening] Fix header comments [NFC]

Author: xwu

stdlib/private/SwiftPrivateThreadExtras/SwiftPrivateThreadExtras.swift

@@ -1,8 +1,8 @@
-//===--- SwiftPrivateThreadExtras.swift ----------------------------------===//
+//===--- SwiftPrivateThreadExtras.swift -----------------------------------===//
 //
 // This source file is part of the Swift.org open source project
 //
-// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Copyright (c) 2014 - 2018 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See https://swift.org/LICENSE.txt for license information

stdlib/private/SwiftPrivateThreadExtras/ThreadBarriers.swift

@@ -1,8 +1,8 @@
-//===--- ThreadBarriers.swift --------------------------------------------===//
+//===--- ThreadBarriers.swift ---------------------------------------------===//
 //
 // This source file is part of the Swift.org open source project
 //
-// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Copyright (c) 2014 - 2018 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See https://swift.org/LICENSE.txt for license information

stdlib/public/Platform/winsdk.modulemap

@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift.org open source project
 //
-// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Copyright (c) 2014 - 2018 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See https://swift.org/LICENSE.txt for license information