py: Add MP_ROM_* macros and mp_rom_* types and use them.
diff --git a/py/objgenerator.c b/py/objgenerator.c
index 59ca6b8..25c31a5 100644
--- a/py/objgenerator.c
+++ b/py/objgenerator.c
@@ -227,10 +227,10 @@
 
 STATIC MP_DEFINE_CONST_FUN_OBJ_1(gen_instance_close_obj, gen_instance_close);
 
-STATIC const mp_map_elem_t gen_instance_locals_dict_table[] = {
-    { MP_OBJ_NEW_QSTR(MP_QSTR_close), (mp_obj_t)&gen_instance_close_obj },
-    { MP_OBJ_NEW_QSTR(MP_QSTR_send), (mp_obj_t)&gen_instance_send_obj },
-    { MP_OBJ_NEW_QSTR(MP_QSTR_throw), (mp_obj_t)&gen_instance_throw_obj },
+STATIC const mp_rom_map_elem_t gen_instance_locals_dict_table[] = {
+    { MP_ROM_QSTR(MP_QSTR_close), MP_ROM_PTR(&gen_instance_close_obj) },
+    { MP_ROM_QSTR(MP_QSTR_send), MP_ROM_PTR(&gen_instance_send_obj) },
+    { MP_ROM_QSTR(MP_QSTR_throw), MP_ROM_PTR(&gen_instance_throw_obj) },
 };
 
 STATIC MP_DEFINE_CONST_DICT(gen_instance_locals_dict, gen_instance_locals_dict_table);