avoid infinite recursion during doc lookup

Author: qunaibit

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/objects/cext/capi/ToNativeTypeNode.java

@@ -321,7 +321,7 @@ static void initializeType(PythonClassNativeWrapper obj, Object mem,
             writeI64Node.write(mem, CFields.PyTypeObject__tp_flags, getTypeFlagsNode.execute(clazz));
 
             // return a C string wrapper that really allocates 'char*' on TO_NATIVE
-            Object docObj = getAttrNode.execute(clazz, SpecialAttributeNames.T___DOC__);
+            Object docObj = clazz.getAttribute(SpecialAttributeNames.T___DOC__);
             if (docObj instanceof TruffleString) {
                 docObj = new CStringWrapper((TruffleString) docObj);
             } else if (docObj instanceof PString) {