* vm_eval.c (eval_string_with_cref): copy cref to limit the scope of
  refienements in the eval string. [ruby-core:56329] [Bug #8722]

* test/ruby/test_refinement.rb: related test.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@42396 b2dd03c8-39d4-4d8f-98ff-823fe69b080e