Port and integrate the irregexp engine from V8

tests/language/regex/backreferences_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("Test to ensure correct behaviour when using backreferences in a RegExp");
+
+  shouldBeTrue(new RegExp(r"(...)\1$").hasMatch('abcabc'));
+  shouldBeFalse(new RegExp(r"(...)\1$").hasMatch('abcdef'));
+  shouldBeFalse(new RegExp(r"(...)\2$").hasMatch('abcabc'));
+  shouldBeFalse(new RegExp(r"(...)\2$").hasMatch('abc'));
+  shouldBeTrue(new RegExp(r"\1(...)$").hasMatch('abcabc'));
+  shouldBeTrue(new RegExp(r"\1(...)$").hasMatch('abcdef'));
+  shouldBeFalse(new RegExp(r"\2(...)$").hasMatch('abcabc'));
+  shouldBeFalse(new RegExp(r"\2(...)$").hasMatch('abc'));
+  shouldBeTrue(new RegExp(r"\1?(...)$").hasMatch('abc'));
+  shouldBeTrue(new RegExp(r"\1?(...)$").hasMatch('abc'));
+
+  var re = new RegExp(r"[^b]*((..)|(\2))+Sz", caseSensitive: false);
+
+  shouldBeFalse(re.hasMatch('axabcd'));
+  shouldBeTrue(re.hasMatch('axabcsz'));
+}