Add facility to Syslog::Logger.

* ext/syslog/lib/syslog/logger.rb (Syslog::Logger): Add facility
  to Syslog::Logger. [Fixes GH-305] patch by Max Shytikov
  https://github.com/ruby/ruby/pull/305

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@42195 b2dd03c8-39d4-4d8f-98ff-823fe69b080e