TODO items.
o use real entropy to make random (ID, port) numbers more random.
o in production mode, do not free memory on exit. In debug mode, test leaks.
o profile memory allocation, and if performance issues, use special memory
  allocator. For example, with caches per thread.
o #define BIT_... different on bigendian and smallendian systems so that
  the htons on flags is not needed to send a message from the cache.
o speed up pkt domain name decompression loop detection using counter perhaps.
o detect OS/400 pthreads implementation that allows upgrading to writelock
  on pthreads rwlocks and use it to examine-rd before storing-wr rrset cache.
o understand synthesized DNAMEs, so those TTL=0 packets are cached properly.
o understand NSEC/NSEC3, aggressive negative caching, so that updates to
  NSEC/NSEC3 will result in proper negative responses.
o fallback without EDNS if result is NOTIMPL, now only on FORMERR like in java.
o scrubber has slow pkt_subdomain and pkt_strict_subdomain functions.
o get serverselection algorithm out of local optimum.
  make subtargets to get rtt info for a couple of targets, like fetch-policy.
  or send out multiple queries to multiple servers.
o donotqueryaddresses allow specification of subnets, use trie to store.
  extend default list to contain illegal ip4 and ip6 addresses.
o memory profile; and if needed put serviced queries under qstate->region
  and special purpose region code, reuse blocks, shrink if too big.
o check query, option to enforce presence of qdsection in noerror answers.
o configuration option where port 53 is used for send and receive, no other
  ports are used.
o (option) to not send replies to clients after a timeout of (say 5 secs) has
  passed, but keep task active for later retries by client.
o private TTL feature
o pretend-dnssec-unaware, and pretend-edns-unaware modes for debug/workshops.
o delegpt use rbtree for ns-list, to avoid slowdown for very large NS sets.
o be able to have different listen and query-to addresses to bind to,
  so you can listen to localhost and query-to to the internet.
o reprime and refresh oft used data before timeout.
o retain prime results in a overlaid roothints file.
o store primed key data in a overlaid keyhints file (sort of like drafttimers).
o windows version, auto update feature, a query to check for the version.
o autoreport of problems
o logrotation, syslog
o command the server with TSIG inband. get-config, clearcache, 
	get stats, get memstats, get ..., reload, clear one zone from cache
o watch for spoof nearmisses.
o improve compression of DNS packets by first puttig uncompressible rrs, then
  compress to their rdata.
o if one server is not responsive do not spend 75 secs on that server, but
  try other servers with lower rtt.
o NSID rfc 5001 support.
o timers rfc 5011 support.
o Treat YXDOMAIN from a DNAME properly, in iterator (not throwaway), validator.
o grab ports nonconsequtive and change the set after a while (change within
  a given range). Could be bad for OS if wrong port. unsure if it helps secure.
o make timeout backoffs randomized (a couple percent random) to spread traffic.
o inspect date on executable, then warn user in log if its more than 1 year.
o proactively prime root, stubs and trust anchors, feature.
  early failure, faster on first query, but more traffic.
o use privilege separation, to change privilege options during reload securely
  not needed.
o check if for PowerDNS(2.9.21) CNAME in Answer section & rcode=NXDOMAIN needs
  to be fixed up to be rcode=NOERROR?
o On Windows use CryptGenRandom() to get random seed for arc4random.