Add support for axfr_ips and PTR records in Linode DNS v4#2134

ChihweiLHBird wants to merge 3 commits intoapache:trunkapache/libcloud:trunkfrom

ChihweiLHBird:zhiwei/linode-dns-updateChihweiLHBird/libcloud:zhiwei/linode-dns-updateCopy head branch name to clipboard