object.c: no TypeError at special const dup
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@56906 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
object.c: no TypeError at special const dup
constants, and return itself instead. [Feature#12979]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@56906 b2dd03c8-39d4-4d8f-98ff-823fe69b080e