Major rewrite of the DNS server and domain handling code.

This should be largely transparent, but it drastically
improves performance and reduces memory foot-print when
configuring large numbers domains of the form
local=/adserver.com/
or
local=/adserver.com/#

Lookup times now grow as log-to-base-2 of the number of domains,
rather than greater than linearly, as before.
The change makes multiple addresses associated with a domain work
address=/example.com/1.2.3.4
address=/example.com/5.6.7.8
It also handles multiple upstream servers for a domain better; using
the same try/retry alogrithms as non domain-specific servers. This
also applies to DNSSEC-generated queries.

Finally, some of the oldest and gnarliest code in dnsmasq has had
a significant clean-up. It's far from perfect, but it _is_ better.

src/dbus.c

@@ -377,7 +377,7 @@ static DBusMessage* dbus_read_servers_ex(DBusMessage *message, int strings)
       /* 0.0.0.0 for server address == NULL, for Dbus */
       if (addr.in.sin_family == AF_INET &&
           addr.in.sin_addr.s_addr == 0)
-        flags |= SERV_NO_ADDR;
+        flags |= SERV_LITERAL_ADDRESS;
       
       if (strings)
 	{