rbldns specific data patch

http://qmail.jms1.net/djbdns/rbldns-patch.shtml
http://qmail.jms1.net/djbdns/djbdns-1.05-rbldns-specific-data.patch

This patch extends the rbldns program to allow the user to specify different
IP addresses and TXT messages to be served in response to DNS queries. The
format of the data file has been modified to allow a returned IP address and
TXT comment to be specified for each IP block. The fields, as seems to be the
standard with the djbdns programs, are separated with colons
(the ":" character.)

For example, if you're operating an RBL which returns 127.0.0.2 for known
spammers, 127.0.0.3 for open relays, and 127.0.0.4 for dialup IP blocks, your
data file might look something like this:

:127.0.0.2:Known spammer at $
10.0.0.0/8
127.0.0.2:127.0.0.2:Test entry
172.16.0.0/12:127.0.0.3:Open relay on $
192.168.0.0/16:127.0.0.4:Dialup user on $
210.0.0.0/8:127.0.0.2
211.0.0.0/8:127.0.0.2:

Lines with no IP address or TXT comment specified (like the "10" line above)
will cause rbldns to return the "default" values (from the ":" line.) This is
identical to how the stock rbldns works, and should allow existing
installations to work with no changes to existing data files.

Lines with an IP address specified but no TXT comment (like the "210" and
"211" lines above) will have an empty TXT record returned, overriding any
default TXT value. In this case the colon after the returned IP is optional.

Signed-off-by: Giam Teck Choon <giamteckchoon@gmail.com>