Remove Syslog#inspect and have only Syslog.inspect.

* ext/syslog/syslog.c (Init_syslog): Define inspect as a singleton
  method and remove it as an instance method. [Bug #6502]


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39316 b2dd03c8-39d4-4d8f-98ff-823fe69b080e