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

tests/standalone/src/package/PackageTest.packages/lib2/lib2.dart

Index: tests/standalone/src/package/PackageTest.packages/lib2/lib2.dart
diff --git a/tests/standalone/src/package/PackageTest.packages/lib2/lib2.dart b/tests/standalone/src/package/PackageTest.packages/lib2/lib2.dart
new file mode 100644
index 0000000000000000000000000000000000000000..51c79cbc2688ad1a63d292a7312f8053b34fa0f4
--- /dev/null
+++ b/tests/standalone/src/package/PackageTest.packages/lib2/lib2.dart
@@ -0,0 +1,12 @@
+// 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('lib2');
+
+#import('package:shared.dart');
+#import('package:lib3/sub/lib3.dart');
+
+void lib2() {
+  output += '|lib2';
+  lib3();
+}