JS backend: support object declaration in other declarations.

#KT-2696 fixed

(cherry picked from commits 8931d13, 627b100 and f6b8686)

js/js.tests/test/org/jetbrains/k2js/test/semantics/ObjectTest.java

@@ -41,12 +41,10 @@ public final class ObjectTest extends SingleFileTranslationTest {
         fooBoxTest();
     }
 
-    //TODO: KT-2696
-    public void TODO_testObjectInObject() throws Exception {
+    public void testObjectInObject() throws Exception {
         fooBoxTest();
     }
 
-
     public void testObjectInheritingFromATrait() throws Exception {
         fooBoxTest();
     }