erb: suppress warnings

* bin/erb (ERB::Main#run): get rid of shadowing outer local
  variables.  [ruby-core:65772] [Feature #10395]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@48788 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* 2014-12-13

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@48789 b2dd03c8-39d4-4d8f-98ff-823fe69b080e