Port and integrate the irregexp engine from V8

tests/language/regex/constructor_test.dart

+// Copyright (c) 2014, 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.
+
+import 'util.dart';
+import 'package:expect/expect.dart';
+
+void main() {
+  description("This test checks use of the regexp constructor.");
+
+  var re = new RegExp(r"abc");
+
+  shouldBeTrue(identical(re, new RegExp(r"abc")));
+  shouldBeTrue(identical(re, new RegExp(r"abc", caseSensitive: true, multiLine: false)));
+  shouldBeFalse(identical(re, new RegExp(r"abc", caseSensitive: false, multiLine: true)));
+  shouldBeFalse(identical(re, new RegExp(r"abc", caseSensitive: true, multiLine: true)));
+  shouldBeFalse(identical(re, new RegExp(r"abc", caseSensitive: false, multiLine: false)));
+}