skipping over last/root label returns a pointer to a memory after domain name, this is unsafe

this doesn’t guarantee valid cache after crash,
but then it’s a cache. most of the time on cold
cache is spent on fsyncing as it’s done per each
commit (=> resolved query)

this also fails if the timeout timer cannot be started,
as it would wait for undefined time otherwise

amalgamated build concatenates all files into a single .c file to
allow compiler see all symbols and produce possibly smaller code.
for binary distributions this is what you want, as it's faster but
may consume more memory during compilation.
it however cannot do incremental builds.

if the NSLIST already has a candidate with addresses, never replace
current leader with an empty one. otherwise if the former leader address
was tried and failed, new empty leader would be blamed for this and
penalized

policy has policy.todnames() for table of names