swithc id_table data structure.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@57416 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
swithc id_table data structure.
by Yura Sokolov. For more detail measurements, see [Feature #12180]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@57416 b2dd03c8-39d4-4d8f-98ff-823fe69b080e