mruby-range-ext/range.c: use the reference from mrb structure.
Avoid `mrb_class_get()` if possible.
@@ -192,7 +192,7 @@ range_size(mrb_state *mrb, mrb_value range)
void
mrb_mruby_range_ext_gem_init(mrb_state* mrb)
{
- struct RClass * s = mrb_class_get(mrb, "Range");
+ struct RClass * s = mrb->range_class;
mrb_define_method(mrb, s, "cover?", range_cover, MRB_ARGS_REQ(1));
mrb_define_method(mrb, s, "size", range_size, MRB_ARGS_NONE());
