[modules] Do basic linking.

test/mjsunit/modules-imports5.js

Index: test/mjsunit/modules-imports5.js
diff --git a/test/mjsunit/modules-this.js b/test/mjsunit/modules-imports5.js
similarity index 68%
copy from test/mjsunit/modules-this.js
copy to test/mjsunit/modules-imports5.js
index 2c8fc74fe75aec57d5ab0df2370edbd43ed3a988..b494c7e1a76327453594512cebf138927ccce9fc 100644
--- a/test/mjsunit/modules-this.js
+++ b/test/mjsunit/modules-imports5.js
@@ -1,7 +1,9 @@
 // Copyright 2016 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
-
+//
 // MODULE
 
-assertEquals(undefined, this);
+import {a} from "modules-skip-3.js";
+export var b = 20;
+assertEquals(42, a+b);