libuv doesn't do connected UDP sockets, so we can't get ICMP unreachable
otherwise

before root hints were hardcoded to the resolver,
now they are present in form of a cut in the resolution
context, and the modules can add/remove/replace them
on the fly

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