lib/webrick/log.rb: sanitize any type of logs

It had failed to sanitize some type of exception messages.  Reported and
patched by Yusuke Endoh (mame) at https://hackerone.com/reports/223363

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@59897 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/webrick/log.rb

@@ -118,10 +118,10 @@ module WEBrick
     # * Otherwise it will return +arg+.inspect.
     def format(arg)
       if arg.is_a?(Exception)
-        "#{arg.class}: #{arg.message}\n\t" <<
+        "#{arg.class}: #{AccessLog.escape(arg.message)}\n\t" <<
         arg.backtrace.join("\n\t") << "\n"
       elsif arg.respond_to?(:to_str)
-        arg.to_str
+        AccessLog.escape(arg.to_str)
       else
         arg.inspect
       end