lib/logger.rb: use %N
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47271 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
lib/logger.rb: use %N
[Fix GH-704]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47271 b2dd03c8-39d4-4d8f-98ff-823fe69b080e