this allows list-like declaration of bound interfaces

e.g. net = { ‘127.0.0.1’, net.eth0 }

the cache can be setup declaratively with:

cache.size = 10 * MB

the cache storage backend can be changed with:

cache.storage = ‘lmdb://.'

module api can now store userdata, e.g. owner

the TCP allowed parallel processing of multiple requests over
one client socket, however if the client socket disconnected,
it left the running tasks reading from bad handle
now each task takes ownership of the handle until it is finished,
only then it is returned to the loop and closed

the pktcache introduces two cache tags PKT/SEC for
basic/DNSSEC responses and stores negative answers in
the cache

previously producers in overlay could only generate query or
update the final answer - this required exported callbacks
from iterate.c and specific processing. this wouldn’t work
for negative cache, as it would be required to reimplement
whole iterate layer for cached data

the new workflow allows produce layers to generate answer
instead, this answer is then consumed in the next step
by the iterate module in unified fashion for all caches/generators