ipfilter: Restore ipfsync
ipfsync is a WIP sync daemon designed to be used in a failover scenario.
It was removed by 5ee61c7daa511927aae8652d6a3ea78866a50ef8. This commit
restores its three files. ipfsync is in my work queue.
MFC after: 10 days
X-MFC with: 5ee61c7daa511927aae8652d6a3ea78866a50ef8