class.c, vm_insnhelper.c: check unknown keywords

* class.c (rb_get_kwargs): if optional is negative, unknown
  keywords are allowed.
* vm_insnhelper.c (vm_callee_setup_keyword_arg): check unknown
  keywords.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@44069 b2dd03c8-39d4-4d8f-98ff-823fe69b080e