Remove all the code and tests which support non-zero stale-answer-client-timeout values, and adjust the documentation.
Explicitly use an empty 'trust-anchors' statement in the system tests where it was used implicitly before. In resolver/ns5/named.conf.in use the trust anchor in 'trusted.conf', which was supposed to be used there.
Check if clients-per-query quota works as expected with or without a positive stale-answer-client-timeout value and serve-stale answers enabled.