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.

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.

If stdout is buffered, kr_log_info() might take ages to show up in the
output stream.  Since this stream could be interleaved with stderr
(e.g. kr_log_error()), it would be good to be able to see the messages
in the order in which they are generated.

breathe failed to process the typedef thinking
the macro expansion was a function pointer

the field length is platform-dependent

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

rdata may be <=64k + 8B on stack which may be source of various mystery
errors later, for example in bindings or stackspace-constricted env

as the libknot packet interface disallows out-of-order packet
writes, authority and additional records must be written after
the answer is complete; records in the rr arrays will be written to final answer during finalization

previously, debug messages were optional with -DWITH_DEBUG
now the debug messages are built in (unless compiled with -DNDEBUG), but
disabled by default

verbose output can be enabled by '-v' or '--verbose' CLI option
or interactively by 'verbose(true|false)' (or in config)

module can identify clients based on their source address or used TSIG
key

the requestor can provide information identifying the query originator
here (address and TSIG key), both fields are optional
update Lua FFI bindings

based on _BSD_SOURCE timersub macro

this is a first step of leaning towards LuaJIT.
the FFI bindings are much faster, simpler and don’t abort traces

daemon core scripting engine is still going to support interpreted Lua, but modules requiring library bindings (such as ‘block’) will require LuaJIT for FFI

previously cryptolib random function was used to generate message id,
this works well but it is slow especially when the entropy is low,
replaced with cryptographically safe prng ISAAC

the ccan directory is going to be used in the future, as it's include
structure makes it easy to embed C snippets instead of reimplementing
them