this fixes a bug when a text-declared type wasn’t reused and LJ eventually segfaulted in ffi.new after a lot of redeclarations

fixes #42

this module allows to rewrite address ranges in answers to different address ranges specified in configuration

this is Unbound's 'forward-zone' on steroids

resolved() returns true if current query is resolved (i.e. authoritative)
final() returns true if current query is resolved and is not a subrequest (has no parent)

this yields much better contrast in this situation, where
one country overshadows the rest on a linear scale

in case the address matches multiple names, the lexicographically first domain name is returned

meaning
\5host1\3com is after \5host1\2cz
\5host2 is after \5host1
\3aaa is after \2zz

current processed query is always in `request->current_query`

if the query has RD=0 or is ANY, only cache is probed
for ANY, only A/AAAA/MX is checked and no query is
forwarded to the authoritatives

- can query cache for records
- can remove only domain or subtree from cache
- can remove data in packet cache or other prefixes
- cache clear also reset NS reputation tracking

same for LDFLAGS. this fixes common problem where CFLAGS after make
was evaluated as a make variable and replaced the default, while
before as env variable and was prepended to the default string.
now they both behave as an env. variable

this is useful if we want to prefetch or update data
in cache, it doesn’t affect the lookup of closest known
zone cut