Port and integrate the irregexp engine from V8

tests/language/regex/regress-6-9-regexp_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';
 
-int main() {
-  var a = [1,2,3][2];
-  switch (a) {
-    case 0.0:            /// 01: compile-time error
-      print("illegal");  /// 01: continued
-    case 1:
-      print("OK");
-  }
-}
+void main() {
+  // Check that the perfect mask check isn't overly optimistic.
+
+  assertFalse(new RegExp(r"[6-9]").hasMatch('2'));
+}