insns.def: refactor by wanabe

* insns.def (defined): use vm_search_superclass() like as normal super
  call.  based on a patch <https://gist.github.com/wanabe/5520026> by
  wanabe.
* vm_insnhelper.c (vm_search_superclass): return error but not raise
  exceptions.
* vm_insnhelper.c (vm_search_super_method): check the result of
  vm_search_superclass and raise execptions on error.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@40584 b2dd03c8-39d4-4d8f-98ff-823fe69b080e