Now that we renamed "debug" to "verbose", the old name didn't seem very
suitable anymore; this new identifier haven't got to master yet.

Split NDEBUG to NDEBUG (asserts) and NOVERBOSELOG (verbose logging); rename all related symbols to use VERBOSE instead of DEBUG

In particular, don't require to call an externally defined function to
find if in --verbose mode or not.  Now it's just an extern bool.
I'm confident the performance impact of not using -DNLOGDEBUG should be
negligible now.

This comes with a small incompatible API+ABI change, but that shouldn't
matter as we've had a couple of those already since the last release.

This reverts commit 64f80706.
TL;DR: it brought almost no benefits AFAIK and potential for problems.

The "portable bytecode" produced by luajit isn't compatible when
(lib)luajit version changes or when some build-time configuration of it
changes.  If you mix these up, kresd fails to start.

It seems a bit cleaner, though impact on size and load speed should not
be noticeable.  We simply install most of the lua code, as before, and I
assume that we *do* want to keep that visibility, at least by default.
Suggested on !57.

The implementation is now similar to set-associative caches
that x86 CPU use.  Also the API is changed a bit, leading to
slight simplification of our use patterns.

Fixes https://gitlab.labs.nic.cz/knot/resolver/issues/93.
API of a KR_EXPORT function is changed, so ABIVER is bumped.

and set libknot_SONAME and libzscanner_SONAME as lua literals.

Remove now obsolete libpath lua function - use find_soname from
platform.mk to define <arg>_SONAME, add lua_pushliteral to
daemon/engine.c and add -D to daemon/daemon.mk for any new library
loaded from Lua.

Use ENABLE_cookies=yes variable to compile functionality.

forks are connected with IPC pipes to process
group leader and can execute expressions on its
behalf. so running commands over all workers
is easy now:

> hostname() -- single
localhost

> map 'hostname()' -- all
localhost
localhost
localhost

string encoded integers are treated as possible
numbers, so a more strict typecheck is needed

this allows embedding other event loops or just
asynchronous events triggered by socket activity.
this is required for things like cooperative
HTTP server, monitoring endpoint or remote
configuration daemon/controller

this change introduces new API for cache backends,
that is a subset of knot_db_api_t from libknot
with several cache-specific operations

major changes are:
* merged 'cachectl' module into 'cache' as it is
  99% default-on and it simplifies things
* not transaction oriented, transactions may be
  reused and cached for higher performance
* scatter/gather API, this is important for
  latency and performance of non-local backends
  like Redis
* faster and reliable cache clearing
* cache-specific operations (prefix scan, ...) in
  the API not hacked in
* simpler code for both backends and caller

the daemon has now three modes of strictness
checking from strict to permissive.
it reflects the tradeoff between resolving the
query in as few steps as possible and security
for insecure zones

an internal timer walks RTT timer periodically and
clears entries with bad results every 5 minutes.
this means that a timeouted entry penalty is 
capped to that interval, making sure that the
bad reputation doesn't last forever

this includes default configuration, resolver
starts completely blank

this is not going to be backwards compatible change, but it will be the first tagged libknot release sufficient for resolver

* PIE,RELRO+NOW and other security features enabled
* support for both static/dynamic builds with BUILDMODE
* dynamic library is ABI-versioned, starting at 1
* pkg-config file is installed

this is needed to make sure it always compiles with PIC

this allows to override any dstdir variable without
patching config.mk

if the root key file doesn’t exist, it will be populated from root DNSKEY query, which will be validated against root trust anchors retrieved over HTTPS with IANA cert verification against built-in current IANA cert CA. it requires luasocket and luasec for it to work. trust anchors XML file signature is not checked, as there’s no facility for PKCS7 checking yet.

this doesn’t guarantee valid cache after crash,
but then it’s a cache. most of the time on cold
cache is spent on fsyncing as it’s done per each
commit (=> resolved query)