vm_eval.c: Check_TypedStruct

* vm_eval.c (eval_string_with_cref): check by Check_TypedStruct
  instead of rb_obj_is_kind_of.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@42108 b2dd03c8-39d4-4d8f-98ff-823fe69b080e