Revert "Add some support for the code-point code-unit distinction."

tests/corelib/reg_exp_unicode_test.dart

-// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-// Dart test for testing regular expressions in Dart.
-
-main() {
-  String str = "\u{10000}";
-
-  // Dot will match surrogates too (ideally it should match a pair).
-  Expect.isTrue(new RegExp(r'^..?$').hasMatch(str));
-
-  // Surrogate pair in a RegExp.
-  Expect.isTrue(new RegExp('^\u{10000}\$').hasMatch(str));
-
-  // Mormon characters should work too.
-  String mitt = "My name is 𐐣𐐮𐐻";
-  Expect.isTrue(new RegExp(r'𐐣𐐮𐐻$').hasMatch(mitt));
-
-  // Character classes sort of work, but the surrogates are treated as separate
-  // characters.
-  Expect.isTrue(new RegExp(r'[𐐣𐐮𐐻]+$').hasMatch(mitt));
-}