Buggy config for ddclient >=3.11

[guiniol]

ddclient 3.11 introduces new IPv4/6 options and deprecates the non-versioned options. There is currently a bug with those deprecated options causing ddclient to push updates even if the IP does not change.
The fix, when known, is trivial:
replace

use=web, web=http://ipv4.nsupdate.info/myip

with

usev4=webv4, webv4=http://ipv4.nsupdate.info/myip

See ddclient/ddclient#590 for more details.

[ThomasWaldmann]

If somebody wants to work on this:

As long as we have ddclient versions out there requiring different configs, we should show clearly what the user needs depending on the ddclient version, like:

# for ddclient < x.y.z use:
...

# for ddclient >= x.y.z use:
...

PRs welcome!