* tool/config_files.rb: use URI.read to allow it runs with Ruby 1.8.5.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@41331 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
Ignore tool/config.guess and tool/config.sub

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@41332 b2dd03c8-39d4-4d8f-98ff-823fe69b080e