Port and integrate the irregexp engine from V8

tests/language/regex/unicode-handling_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 proper handling of Unicode RegExps and <a href="http:new RegExp(r"/bugzilla.webkit.org/show_bug.cgi?id=7445">bug 7445<")a>: Gmail puts wrong subject in replies.'
+  );
+
+  // Regex to match Re in various languanges straight from Gmail source
+  var I3=new RegExp(r"^\s*(fwd|re|aw|antw|antwort|wg|sv|ang|odp|betreff|betr|transf|reenv\.|reenv|in|res|resp|resp\.|enc|\u8f6c\u53d1|\u56DE\u590D|\u041F\u0435\u0440\u0435\u0441\u043B|\u041E\u0442\u0432\u0435\u0442):\s*(.*)$", caseSensitive: false);
+
+  // Other RegExs from Gmail source
+  var Ci=new RegExp(r"\s+");
+  var BC=new RegExp(r"^ ");
+  var BG=new RegExp(r" $");
+
+  // This function replaces consecutive whitespace with a single space
+  // then removes a leading and trailing space if they exist. (From Gmail)
+  dynamic Gn(a) {
+      return a.replaceAll(Ci, " ").replaceAll(BC, "").replaceAll(BG, "");
+  }
+
+  // Strips leading Re or similar (from Gmail source)
+  dynamic cy(a) {
+      //var b = I3.firstMatch(a);
+      var b = I3.firstMatch(a);
+
+      if (b != null) {
+          a = b.group(2);
+      }
+
+      return Gn(a);
+  }
+
+  assertEquals(cy('Re: Moose'), 'Moose');
+  assertEquals(cy('\u8f6c\u53d1: Moose'), 'Moose');
+
+  // Test handling of \u2820 (skull and crossbones)
+  var sample="sample bm\u2820p cm\\u2820p";
+
+  var inlineRe=new RegExp(r".m\u2820p");
+  assertEquals(inlineRe.firstMatch(sample).group(0), 'bm\u2820p');
+
+
+  // Test handling of \u007c "|"
+  var bsample="sample bm\u007cp cm\\u007cp";
+
+  var binlineRe=new RegExp(r".m\u007cp");
+
+  assertEquals(binlineRe.firstMatch(bsample).group(0), 'bm|p');
+}