* lib/rubygems: Update to RubyGems 2.0.13. [ruby-core:58031]
  [Backport #9052]
  the patch is provided by drbrain (Eric Hodel).


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_0_0@43435 b2dd03c8-39d4-4d8f-98ff-823fe69b080e