NFC: Add missing copyright headers.

Add missing copyright headers in Options/Options.swift and Utilities/PrefixTrie.swift.

Author: rxwei

Sources/SwiftDriver/Options/Options.swift

@@ -1,3 +1,14 @@
+//===--------------- Options.swift - Swift Driver Options -----------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2019 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
+//
+//===----------------------------------------------------------------------===//
 
 extension Option {
   public static let INPUT: Option = Option("<input>", .input, attributes: [.argumentIsPath])

Sources/SwiftDriver/Utilities/PrefixTrie.swift

@@ -1,3 +1,15 @@
+//==------------------ PrefixTrie.swift - Prefix Trie ---------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2019 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
+//
+//===----------------------------------------------------------------------===//
+
 /// A prefix trie is a data structure for quickly matching prefixes of strings.
 /// It's a tree structure where each node in the tree corresponds to another
 /// element in the prefix of whatever you're looking for.