[gardening] Add missing copyright notice

Author: practicalswift

stdlib/public/core/ThreadLocalStorage.swift

@@ -1,3 +1,14 @@
+//===--- ThreadLocalStorage.swift -----------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2017 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
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
 import SwiftShims
 
 // For testing purposes, a thread-safe counter to guarantee that destructors get