When you change this to true, you may need to add more tests.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@53141 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
and st_delete_safe. patched by Sokolov Yura at
https://github.com/ruby/ruby/pull/84
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@34963 b2dd03c8-39d4-4d8f-98ff-823fe69b080e