1. choose shift-and-xor hash because it does not use multiply and is
   faster than bernstain during profiling
2. better boundary check for normalize_domain_name
3. change hash table % to bit &

variable for IPV6 was ignored until test build a full feature debian package
found the problem.

--server without ip address means the domain is local and the query should not
be forwarded to upstream servers

add a void *obj to contain any pointer.