unix microsocket: Add dummy makefile() method.
Unlike CPython socket, microsocket object already implements stream protocol
(read/write methods), so makefile() just returns object itself. TODO: this
doesn't take care of arguments CPython's makefile() may accept.
diff --git a/py/obj.h b/py/obj.h
index f99bcc4..85462b3 100644
--- a/py/obj.h
+++ b/py/obj.h
@@ -370,6 +370,7 @@
void mp_obj_fun_bc_get(mp_obj_t self_in, int *n_args, uint *n_state, const byte **code);
mp_obj_t mp_identity(mp_obj_t self);
+MP_DECLARE_CONST_FUN_OBJ(mp_identity_obj);
// super
extern const mp_obj_type_t super_type;