first, and disable EDNS in a second round.  This adds some latency
(one more roundtrip), but it's safer to not drop EDNS0 on a first
failure.

Fixes #129.  CNAMEs could get broken before this commit.

The change of `cut->name` to `current_cut` should cause no real change,
but the meaning seems more cleaner this way.

layer/iterate: change the order of records in the answer when CNAME refers to the record that we already have

... at least until we implement (some of) them correctly.

At least until we implement them properly.

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

- The API and ABI for modules changes slightly (details below).
  KR_MODULE_API is bumped to avoid loading incompatible code.
  We have bumped libkres ABIVER since the last release 1.1.1,
  so leaving that one intact.

- Make KR_STATE_YIELD not reuse 0 value anymore.
  It's easy to e.g. return kr_ok() by mistake.
- struct kr_layer_t:
  * ::mm was unused, uninitialized, etc.
  * Make ::state an int, as it was everywhere else.
  * void *data was ugly and always containing struct kr_request *
- struct kr_layer_api:
  * Drop the void* parameter from ::begin, as it was only used
    for the request which is available as ctx->req anyway
    (formerly ctx->data).
  * Drop ::fail.  It wasn't even called.  Modules can watch for
    KR_STATE_FAIL in ::finish.
- Document the apparent meaning of the layer interface, deduced mainly
  from the way it's used in the code.  Caveats:
  * enum knot_layer_state handling seems to assume that it holds exactly
    one of the possibilities at a time.  The cookie module does NOT
    follow that (intentionally), apparently depending on the exact
    implementation of the handling at that moment.  It feels fragile.
  * I was unable to deduce a plausible description of when ::reset is
    called.  It's practically unused in modules, too.

It causes lots of line changes, but it would be confusing to keep the
current state over long term.

RTT tracking for all targets is also supported,
but no loadbalancing is done based on that yet

REFUSED response no longer causes retry in
iterator when operating in stub mode

Use ENABLE_cookies=yes variable to compile functionality.

The cookies layer injects a new query into the plan when a DADCOOKIE
response is detected. After failing the second attempt a TCP fallback is
signalised.

in normal mode, only final CNAME target is refetched, but
not intermediate CNAMEs. intermediate CNAMEs are *never* cached,
but they are used to get final name for requery. in strict mode now,
every CNAME target is explicitly fetched even if it's a chained CNAME.

this is required to avoid REFUSED loops if the origin doesn't handle
minimisation well

* simplified soft-fail per-ns limit to per-query
  limit, each query gets 4 tries at resolving
* instead of locking at single servfailing NS,
  penalise it and run reelection, this may or
  may not try other servers but avoids pathologic
  case when single NS is servfailing while others
  are good but never probed
* added new nsrep update mode (addition)