Port and integrate the irregexp engine from V8

tests/language/regex/character-match-out-of-order_test.dart

Index: tests/language/regex/character-match-out-of-order_test.dart
diff --git a/tests/language/issue20476_test.dart b/tests/language/regex/character-match-out-of-order_test.dart
similarity index 57%
copy from tests/language/issue20476_test.dart
copy to tests/language/regex/character-match-out-of-order_test.dart
index 35890a672dc6476dd2b20129c02a0d757dbfb945..469f55b1fc76d6069267a80141319165edc530f9 100644
--- a/tests/language/issue20476_test.dart
+++ b/tests/language/regex/character-match-out-of-order_test.dart
@@ -2,23 +2,11 @@
 // 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';
 
-foo() {
-  try {
-    try {
-      return 1;
-    } catch (e1) {
-    } finally {
-      return 3;
-    }
-  } catch (e2) {
-  } finally  {
-    return 5;
-  }
-}
-
+void main() {
+  description('Test to ensure RegExp generates single character matches in the correct order');
 
-main() {
-  Expect.equals(5, foo());
+  shouldBe(new RegExp(r"[\w']+").firstMatch("'_'"), ["'_'"]);
 }