s/ip/ipv4/g because they are ipv4 functions.
  (there's a policy that the name "ip" is for methods which supports
   both ipv4 and ipv6)

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@41034 b2dd03c8-39d4-4d8f-98ff-823fe69b080e