Port and integrate the irregexp engine from V8

tests/language/regex/char-insensitive_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 the case-insensitive matching of character literals."
+  );
+
+  shouldBeTrue(new RegExp(r"\u00E5", caseSensitive: false).hasMatch('new RegExp(r"\u00E5")'));
+  shouldBeTrue(new RegExp(r"\u00E5", caseSensitive: false).hasMatch('new RegExp(r"\u00C5")'));
+  shouldBeTrue(new RegExp(r"\u00C5", caseSensitive: false).hasMatch('new RegExp(r"\u00E5")'));
+  shouldBeTrue(new RegExp(r"\u00C5", caseSensitive: false).hasMatch('new RegExp(r"\u00C5")'));
+
+  shouldBeFalse(new RegExp(r"\u00E5", caseSensitive: false).hasMatch('P'));
+  shouldBeFalse(new RegExp(r"\u00E5", caseSensitive: false).hasMatch('PASS'));
+  shouldBeFalse(new RegExp(r"\u00C5", caseSensitive: false).hasMatch('P'));
+  shouldBeFalse(new RegExp(r"\u00C5", caseSensitive: false).hasMatch('PASS'));
+
+  shouldBeNull(firstMatch('PASS', new RegExp(r"\u00C5", caseSensitive: false)));
+  shouldBeNull(firstMatch('PASS', new RegExp(r"\u00C5", caseSensitive: false)));
+
+  assertEquals('PAS\u00E5'.replaceAll(new RegExp(r"\u00E5", caseSensitive: false), 'S'), 'PASS');
+  assertEquals('PAS\u00E5'.replaceAll(new RegExp(r"\u00C5", caseSensitive: false), 'S'), 'PASS');
+  assertEquals('PAS\u00C5'.replaceAll(new RegExp(r"\u00E5", caseSensitive: false), 'S'), 'PASS');
+  assertEquals('PAS\u00C5'.replaceAll(new RegExp(r"\u00C5", caseSensitive: false), 'S'), 'PASS');
+
+  assertEquals('PASS'.replaceAll(new RegExp(r"\u00E5", caseSensitive: false), '%C3%A5'), 'PASS');
+  assertEquals('PASS'.replaceAll(new RegExp(r"\u00C5", caseSensitive: false), '%C3%A5'), 'PASS');
+}