WEBrick: prevent response splitting and header injection
This is a follow up to d9d4a28.
The commit prevented CRLR, but did not address an isolated CR or an
isolated LF.
Co-Authored-By: NARUSE, Yui <naruse@airemix.jp>
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_4@67819 b2dd03c8-39d4-4d8f-98ff-823fe69b080e