fileutils.rb: [DOC] update rdoc

* lib/fileutils.rb (FileUtils#copy_entry): update rdoc about
  preserve option and permissions, following r31123.
  [ruby-core:62065] [Bug #9748]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45604 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* 2014-04-17

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45605 b2dd03c8-39d4-4d8f-98ff-823fe69b080e