Rework logging.

Rework logging.

Use log.c like in many other daemons, with small additions to maintain
a log queue (useful to dump a single log line with several logging
statements).  Use log.c to dump the internal state, and remove the -R
option (a similar feature will be implemented differently soon).

The end goal is to avoid touching the filesystem and use much tighter
pledge(2) restrictions.

Tested by Freddy Dissaux.