Add static getters for common internet addresses

tests/standalone/io/internet_address_test.dart

+// Copyright (c) 2013, 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 'dart:io';
+
+import "package:expect/expect.dart";
+
+void test() {
+  var loopback4 = InternetAddress.LOOPBACK_IP_V4;
+  Expect.isNotNull(loopback4);
+  Expect.equals(InternetAddressType.IP_V4, loopback4.type);
+  Expect.equals("localhost", loopback4.host);
+  Expect.equals("127.0.0.1", loopback4.address);
+
+  var loopback6 = InternetAddress.LOOPBACK_IP_V6;
+  Expect.isNotNull(loopback6);
+  Expect.equals(InternetAddressType.IP_V6, loopback6.type);
+  Expect.equals("ip6-localhost", loopback6.host);
+  Expect.equals("::1", loopback6.address);
+
+  var any4 = InternetAddress.ANY_IP_V4;
+  Expect.isNotNull(any4);
+  Expect.equals(InternetAddressType.IP_V4, any4.type);
+  Expect.equals("0.0.0.0", any4.host);
+  Expect.equals("0.0.0.0", any4.address);
+
+  var any6 = InternetAddress.ANY_IP_V6;
+  Expect.isNotNull(any6);
+  Expect.equals(InternetAddressType.IP_V6, any6.type);
+  Expect.equals("::", any6.host);
+  Expect.equals("::", any6.address);
+}
+
+void main() {
+  test();
+}