make getLazyPythonClass a library message

Author: timfel

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/objects/object/PythonObject.java

@@ -107,6 +107,7 @@ public final void setLazyPythonClass(PythonAbstractClass cls,
     /**
      * This is usually final, a fact may be optimized further if the storage turns into a constant.
      */
+    @ExportMessage
     public final LazyPythonClass getLazyPythonClass() {
         return storedPythonClass;
     }

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/objects/object/PythonObjectLibrary.java

@@ -66,6 +66,8 @@ public void setDict(PythonAbstractObject receiver, PHashingCollection dict) thro
         throw UnsupportedMessageException.create();
     }
 
+    public abstract void getLazyPythonClass(PythonAbstractObject receiver);
+
     public abstract void setLazyPythonClass(PythonAbstractObject receiver, LazyPythonClass cls);
 
     static final LibraryFactory<PythonObjectLibrary> FACTORY = LibraryFactory.resolve(PythonObjectLibrary.class);