Some items are defined by autoconf methods, others by NUT code (and then often only optionally - defining as 1 if a feature is present).

As a consequence, some features can be flagged by simple #if FLAG while others should pedantically be #if ( defined(FLAG) && (FLAG) ) or some such. Use of #ifdef FLAG falters if it is defined but zero. Use of #if FLAG falters if it is not defined (GCC helps by defaulting it to 0 but generally it is undefined preprocessor behavior). Note that autotools config.h is generated to either #define a token with some value (may be 0 or not), or add a commented-away #undef of the token.

We should recomb the codebase to pick one standard and stick to it, avoiding confusion.