ruby.h: no parent in rb_data_type_t

* error.c (rb_typeddata_is_kind_of, rb_check_typeddata): ditto.
* error.c (rb_typeddata_inherited_p): deprecate. still keep for
  potential binary compatibility.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@48647 b2dd03c8-39d4-4d8f-98ff-823fe69b080e