Add support for importing using "package:" to the standalone VM.

tests/standalone/src/package/PackageTest.dart

+// Copyright (c) 2012, 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.
+#library('package_test');

[nweiz, 2012/04/10 00:22:28]

Nit: Empty line between license comment and #library.

[Bob Nystrom, 2012/04/10 00:57:47]

Done.

+
+#import('package:lib1.dart');
+#import('package:shared.dart');
+
+void main() {
+  output = 'main';
+  // Call an imported lib, which will in turn call some others.
+  lib1();
+
+  // Make sure they were all reached successfully.
+  Expect.equals(output, 'main|lib1|lib2|lib3');
+}