Add mrb_class_get_under()

include/mruby.h

@@ -178,6 +178,7 @@ struct RClass * mrb_class_new(mrb_state *mrb, struct RClass *super);
 struct RClass * mrb_module_new(mrb_state *mrb);
 int mrb_class_defined(mrb_state *mrb, const char *name);
 struct RClass * mrb_class_get(mrb_state *mrb, const char *name);
+struct RClass * mrb_class_get_under(mrb_state *mrb, struct RClass *outer, const char *name);
 
 mrb_value mrb_obj_dup(mrb_state *mrb, mrb_value obj);
 mrb_value mrb_check_to_integer(mrb_state *mrb, mrb_value val, const char *method);

src/class.c

@@ -227,7 +227,13 @@ class_from_sym(mrb_state *mrb, struct RClass *klass, mrb_sym id)
 struct RClass *
 mrb_class_get(mrb_state *mrb, const char *name)
 {
-  return class_from_sym(mrb, mrb->object_class, mrb_intern(mrb, name));
+  return mrb_class_get_under(mrb, mrb->object_class, name);
+}
+
+struct RClass *
+mrb_class_get_under(mrb_state *mrb, struct RClass *outer, const char *name)
+{
+  return class_from_sym(mrb, outer, mrb_intern(mrb, name));
 }
 
 /*!