prefix" address instead - there are so many available with varying
policies that this isn't a good place to list them (and might imply
some kind of recommendation which is not intended).
Particularly prompted by several on the previous list (he.net and opendns)
strip RRSIG from results which cause DNSSEC failures now that validation
is enabled in the example config as noticed by solene@.
While there, shrink qname-minimisation comment to match other nearby
comments, and drop dns64 example which is quite a specialist use case
and not really needed in this basic example.