time_t may overflow mrb_int when word boxing is used

mrbgems/mruby-time/src/time.c

@@ -671,7 +671,7 @@ mrb_time_to_i(mrb_state *mrb, mrb_value self)
   struct mrb_time *tm;
 
   tm = DATA_GET_PTR(mrb, self, &mrb_time_type, struct mrb_time);
-#ifdef MRB_INT16
+#if defined(MRB_INT16) || defined(MRB_WORD_BOXING)
   if (tm->sec > MRB_INT_MAX || tm->sec < MRB_INT_MIN) {
     return mrb_float_value(mrb, (mrb_float)tm->sec);
   }