parse.y: no assigned but unused warnings in eval

* parse.y (local_push_gen): no assigned but unused variable warnings
  in eval as well as -e.  [Feature #7730] [ruby-core:51580]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@38998 b2dd03c8-39d4-4d8f-98ff-823fe69b080e