[modules] Do basic linking.

test/mjsunit/modules-imports3.js

+// 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
+
+import {a as x, a as y} from "modules-skip-1.js";
+import {b as z, get_a, set_a} from "modules-skip-1.js";
+
+assertEquals(1, get_a());
+assertEquals(1, x);
+assertEquals(1, y);
+assertEquals(1, z);
+
+set_a(2);
+assertEquals(2, get_a());
+assertEquals(2, x);
+assertEquals(2, y);
+assertEquals(2, z);
+
+assertThrows(() => x = 3, TypeError);
+assertThrows(() => y = 3, TypeError);
+assertThrows(() => z = 3, TypeError);
+
+assertEquals(2, get_a());
+assertEquals(2, x);
+assertEquals(2, y);
+assertEquals(2, z);
+
+assertEquals(2, eval('get_a()'));
+assertEquals(2, eval('x'));
+assertEquals(2, eval('y'));
+assertEquals(2, eval('z'));
+
+assertEquals(2, (() => get_a())());
+assertEquals(2, (() => x)());
+assertEquals(2, (() => y)());
+assertEquals(2, (() => z)());