git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_3@53898 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
to ensure it's a bignum on all impls.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_3@53898 b2dd03c8-39d4-4d8f-98ff-823fe69b080e