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/dnssec.c

@@ -2230,7 +2230,7 @@ size_t dnssec_generate_query(struct dns_header *header, unsigned char *end, char
 
   p = (unsigned char *)(header+1);
 	
-  p = do_rfc1035_name(p, name);
+  p = do_rfc1035_name(p, name, NULL);
   *p++ = 0;
   PUTSHORT(type, p);
   PUTSHORT(class, p);