Ruby

merge revision(s) 56111: [Backport #12738]

    * array.c (flatten): use rb_obj_class instead of rb_class_of
      because rb_class_of may return a singleton class.
      [ruby-dev:49781] [Bug #12738]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_2@56305 b2dd03c8-39d4-4d8f-98ff-823fe69b080e