hash.c: fix infinite loop

* hash.c (has_extra_methods): traverse ancestors, and fix infinite
  loop.  [Bug #9275]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@44363 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

hash.c

@@ -41,6 +41,7 @@ has_extra_methods(VALUE klass)
     while (c != base) {
 	st_table *mtbl = RCLASS_M_TBL(c);
 	if (mtbl && mtbl->num_entries) return klass;
+	c = RCLASS_SUPER(c);
     }
     return 0;
 }