SQLite BIND SDB driver

The SQLite BIND SDB "driver" is intended as an alternative both to the
pgsqldb and dirdb drivers, for situations that would like the management
simplicity and convenience of single filesystem files, with the additional
capability of SQL databases.  It is also intended as an alternative to
the standard dynamic DNS update capability in bind, which effectively
requires use of DNSSEC keys for authorization and is limited to 'nsupdate'
for updates.  An sqlite database, by contrast, uses and requires only
normal filesystem permissions, and may be updated however a typical SQLite
database might be updated, e.g., via a web service with an SQLite backend.

This driver is not considered suitable for very high volume public
nameserver use, while likely useful for smaller private nameserver
applications, whether or not in a production environment.  It should
generally be suitable wherever SQLite is preferable over larger database
engines, and not suitable where SQLite is not preferable.

Usage:

o Use the named_sdb process ( put ENABLE_SDB=yes in /etc/sysconfig/named )

o Edit your named.conf to contain a database zone, eg.:
  
zone "mydomain.net." IN {
        type master;
        database "sqlite /etc/named.d/mydomain.db mydomain";
        #                ^- DB file               ^-Table
};

o Create the database zone table
  The table must contain the columns "name", "rdtype", and "rdata", and
  is expected to contain a properly constructed zone.  The program
  "zone2sqlite" creates such a table.
  
  zone2sqlite usage:
    
    zone2sqlite origin zonefile dbfile dbtable

    where
	origin   : zone origin, eg "mydomain.net."
	zonefile : master zone database file, eg. mydomain.net.zone
	dbfile   : name of SQLite database file
        dbtable  : name of table in database

---
# mydomain.net.zone:
$TTL 1H
@       SOA     localhost.      root.localhost. (       1
                                                3H
                                                1H
                                                1W
                                                1H )
        NS      localhost.
host1   A       192.168.2.1
host2   A       192.168.2.2
host3   A       192.168.2.3
host4   A       192.168.2.4
host5   A       192.168.2.5
host6   A       192.168.2.6
host7   A       192.168.2.7
---

# zone2sqlite mydomain.net. mydomain.net.zone mydomain.net.db mydomain

will create/update the 'mydomain' table in database file 'mydomain.net.db'.