api level docs?

[Aaron Aston]

> I'm almost there ... it's not that hard.  All I need to figure out now
> is how to remove a resource definition while I'm iterating.  There is
> a handy library function called 'dns_db_dump()' that will let me write
> the filtered db back out to disk.

In the end I had to use the routines invoked by the DDNS side of BIND
to edit out the resource records that I determine to be internal.  In
particular I had to use the stuff from diff.h/.c (dns_diff_init,
dns_difftuple_create, dns_diff_append, dns_diff_apply).

I was trying to manipulate the rbt tree directly, but the code that
manages rdata structs is just not pretty (or is, perhaps, very pretty,
as in the same prettiness as a wasp.  Fiddle with the wrong thing in
there and you're going to get 'stung').

I thought I might have trouble removing records as I iterate, but the
iterators seem to remain valid even though the 'current' record has
been removed.  If this does end up being a problem I will just collect
my diffs as I iterate and then apply one large diff after processing
the zone file.