leakchecker.rb: for older IO.console
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@49106 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
leakchecker.rb: for older IO.console
version IO.console to get rid of ArgumentError, so that older
versions can run to compare the resuls.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@49106 b2dd03c8-39d4-4d8f-98ff-823fe69b080e