Ruby

Document File.{setuid?,setgid?,sticky?} support for IO objects [Bug #13972]

• file.c (rb_file_setuid_p): rdoc for IO object support
  (rb_file_sgid_p): ditto (rb_file_sticky_p): ditto
• NEWS: inform users of new feature
• test/file/test_file_exhaustive.rb (io_open): wrapper for bare IO
  object (test_suid): test for bare IO support (test_sgid): ditto
  (test_sticky): ditto

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@65235 b2dd03c8-39d4-4d8f-98ff-823fe69b080e