Merge rubygems-2.6.14 changes.

	  It fixed http://blog.rubygems.org/2017/10/09/unsafe-object-deserialization-vulnerability.html

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_4@60168 b2dd03c8-39d4-4d8f-98ff-823fe69b080e