lib/dns/zone.c contains multiple functions related to NSEC3 processing:

  - dns_zone_addnsec3chain()
  - dns_zone_setnsec3param()
  - fixup_nsec3param()
  - resume_addnsec3chain()
  - setnsec3param()
  - zone_addnsec3chain()
  - zone_nsec3chain()

The purpose of each of these functions and the relations between them
are far from obvious for an untrained eye and thus they could use some
comments.