Fix rb_copy_generic_ivar and rb_free_generic_ivar specs
Fix rb_copy_generic_ivar and rb_free_generic_ivar specs

* Based on @nobu's help.

ruby/spec,eregon/rubyspec,nobu/rubyspec,ruby/spec,nobu/rubyspec,ruby/spec,eregon/rubyspec,eregon/rubyspec,nobu/rubyspec