Support authoritative 5.x version (#230)

[deric]

Pull Request (PR) description

Support 4.x and 5.x releases for auth (and recursor as well).

This Pull Request (PR) fixes the following issues

• Fixes support for powerdns auth versions 5.x #230

[deric]

@yakatz Could you have a look at this? Thanks!

[anthonysomerset]

FYI i've checked this out and it works and runs fine - its a simple change and i want to say LGTM

[saz]

FYI: Starting with 5.2, the old config file won't be read until --enable-old-settings is set.
We should merge this PR after #234

[deric]

@saz It does make sense to merge this just for 5.0 and 5.1 releases. #234 requires much more changes and this change shouldn't be part of it (but tests would fail it it's not included).

[anthonysomerset]

its worth also pointing out 5.0 is the only stable release in the 5.x train at this time so 5.2 is at least a little ways off approx 12 months as 5.0 was only just released in october so i think we have some ways to go and it seems to me that the better approach is to get this out, then spend the time to get #234 right without there being undue pressure because its seen as blocking this PR (its also dependent on this PR too as well)