prevent rb_cObject from GC
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@55429 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
prevent rb_cObject from GC
class tree root, from GC. [ruby-dev:49666] [Bug #12492]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@55429 b2dd03c8-39d4-4d8f-98ff-823fe69b080e