Security fix, CVE-2017-14491 DNS heap buffer overflow.

Fix heap overflow in DNS code. This is a potentially serious
security hole. It allows an attacker who can make DNS
requests to dnsmasq, and who controls the contents of
a domain, which is thereby queried, to overflow
(by 2 bytes) a heap buffer and either crash, or
even take control of, dnsmasq.

src/rfc3315.c

@@ -1479,10 +1479,10 @@ static struct dhcp_netid *add_options(struct state *state, int do_refresh)
       if ((p = expand(len + 2)))
 	{
 	  *(p++) = state->fqdn_flags;
-	  p = do_rfc1035_name(p, state->hostname);
+	  p = do_rfc1035_name(p, state->hostname, NULL);
 	  if (state->send_domain)
 	    {
-	      p = do_rfc1035_name(p, state->send_domain);
+	      p = do_rfc1035_name(p, state->send_domain, NULL);
 	      *p = 0;
 	    }
 	}