* Core: convert IP addresses to reverse zone
If we see IP/mask syntax and the mask mod 8 == 0 we assume a reverse
zone and convert to in-addr or .arpa.
* typos
* integration test
* Addr is not used
* core: clean up normalize
Create a SplitHostPort function that can be used both from normalize.go
and address.go. This removes some (not all!) duplication between the
both and makes it work with reverse address notations.
* More tests
