Fix to not define outer when outer is itself.

example:
  a = Class.new
  a::A = a

src/class.c

@@ -65,7 +65,7 @@ mrb_class_name_class(mrb_state *mrb, struct RClass *outer, struct RClass *c, mrb
   else {
     name = mrb_class_path(mrb, outer);
     if (mrb_nil_p(name)) {      /* unnamed outer class */
-      if (outer != mrb->object_class) {
+      if (outer != mrb->object_class && outer != c) {
         mrb_obj_iv_set(mrb, (struct RObject*)c, mrb_intern_lit(mrb, "__outer__"),
                        mrb_obj_value(outer));
       }

src/variable.c

@@ -377,8 +377,9 @@ is_namespace(enum mrb_vtype tt)
 static inline void
 assign_class_name(mrb_state *mrb, struct RObject *obj, mrb_sym sym, mrb_value v)
 {
-  if (is_namespace(obj->tt) && is_namespace(mrb_type(v)) && ISUPPER(mrb_sym2name(mrb, sym)[0])) {
+  if (is_namespace(obj->tt) && is_namespace(mrb_type(v))) {
     struct RObject *c = mrb_obj_ptr(v);
+    if (obj != c && ISUPPER(mrb_sym2name(mrb, sym)[0])) {
       mrb_sym id_classname = mrb_intern_lit(mrb, "__classname__");
       mrb_value o = mrb_obj_iv_get(mrb, c, id_classname);
 
@@ -396,6 +397,7 @@ assign_class_name(mrb_state *mrb, struct RObject *obj, mrb_sym sym, mrb_value v)
         }
       }
     }
+  }
 }
 #endif