These functions will be used in the process of replacing fatal(),
check_result(), and fprintf() calls throughout lib/dns/zoneverify.c with
code that does not call exit(). They are intended for:
- zoneverify_log_error(): logging problems encountered while
performing zone verification,
- zoneverify_print(): printing status messages and reports which are
only useful in standalone tools.
To make using dns_zone_logv() possible, add a new "zone" argument to
dns_zoneverify_dnssec() that standalone tools are expected to set to
NULL.