disable rdoc for internal constants [ci skip]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@59484 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ext/pathname/lib/pathname.rb

@@ -14,6 +14,8 @@ require 'pathname.so'
 
 class Pathname
 
+  # :stopdoc:
+
   # to_path is implemented so Pathname objects are usable with File.open, etc.
   TO_PATH = :to_path