KT-449 class object in inner class must be an error

===
class A {
  class B {
    class object { }
  }
}
===

compiler/frontend/src/org/jetbrains/jet/lang/descriptors/MutableClassDescriptor.java

@@ -61,6 +61,9 @@ public class MutableClassDescriptor extends MutableDeclarationDescriptor impleme
     @Override
     public ClassObjectStatus setClassObjectDescriptor(@NotNull MutableClassDescriptor classObjectDescriptor) {
         if (this.classObjectDescriptor != null) return ClassObjectStatus.DUPLICATE;
+        if (!(this.getContainingDeclaration() instanceof NamespaceDescriptor)) {
+            return ClassObjectStatus.NOT_ALLOWED;
+        }
         assert classObjectDescriptor.getKind() == ClassKind.OBJECT;
         this.classObjectDescriptor = classObjectDescriptor;
         return ClassObjectStatus.OK;

compiler/testData/checkerWithErrorTypes/quick/InnerClassClassObject.jet

@@ -0,0 +1,7 @@
+// http://youtrack.jetbrains.net/issue/KT-449
+
+class A {
+    class B {
+        <!CLASS_OBJECT_NOT_ALLOWED!>class object { }<!>
+    }
+}