Merge !92: Change NDEBUG to verbose logging

As requested in !90, I have renamed all *_debug_* and *DEBUG* to verbose
(where it made sense), and renamed NLOGDEBUG to NOVERBOSELOG.

The logic is simple - most usually we want to have verbose logging
compiled in and `assert()` not compiled in (`-DNDEBUG`).

diff --cc lib/layer/validate.c
Simple merge