* lib/securerandom.rb: [DOC] specify arguments passed to ::random_bytes
  By @chastell [Fixes GH-412] https://github.com/ruby/ruby/pull/412


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@43573 b2dd03c8-39d4-4d8f-98ff-823fe69b080e