Port and integrate the irregexp engine from V8

tests/language/regex/bol-with-multiline_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 for beginning of line (BOL or ^) matching in a multiline string</a>'
+  );
+
+  var s = "aced\nabc";
+  shouldBeNull(firstMatch(s, new RegExp(r"^abc")));
+  shouldBe(firstMatch(s, new RegExp(r"^abc", multiLine: true)), ["abc"]);
+  shouldBeNull(firstMatch(s, new RegExp(r"(^|X)abc")));
+  shouldBe(firstMatch(s, new RegExp(r"(^|X)abc", multiLine: true)), ["abc",""]);
+  shouldBe(firstMatch(s, new RegExp(r"(^a|Xa)bc", multiLine: true)), ["abc","a"]);
+}