fixes potential cache key oob write

also some cleanup and version bump to Q2

previously a CNAME RR could be merged as a queried type RR, leading to failed cache lookups as ‘expired’

previously if NS had no A/AAAA records, they we’re looked up in subrequests, after that a new NS was reelected (possibly preferring another unknown), now it stays true to the NS of choice and changes only if it is unuseable

the cache_peek() api was reworked to return an error code instead, from this the caller can tell whether the record is present (but expired) or missing. this save a secondary CNAME lookup in case the original record was just expired

this LRU-like cache tracks lame nameservers, unresolvable
nameservers (to not waste resources in trying to resolve them),
and possibly other features (extension support, …)

if a name server is missing address, it requires launching a recursive query to discover it - starting from root
now however it can start from either closest covering zonecut in cache if it isn’t a subdomain of current zone cut, or as a parent of current zone cut

when a NS is in the TIMEOUT, it can’t be autoselected by default but only probed after a successful dice roll - however in some scenarios we’d like to probe timeouting servers more thoroughly 

simplified bee foraging strategy, by default each query goes to the most rewarding NS
however with a chance proportional to the NS RTT, a server may be probed even if it isn’t the most rewarding

prevents pointless caching of TTL={0,1} records

previously the NS address list was wiped out, this prevents them from being added in the first place

some servers break qname m12n by sending REFUSED, this accepts such answer and requeries with m12n turned off 

score has now meaning of ‘RTT’, maximum RTT is 10s
which is also the penalty for timeout
unknown servers are favorized as 10ms servers to
encourage resolver to try them out, if they contain
unknown glue they are most favourable