pkt: new function to return original wire format QNAME

This commit adds a new function knot_pkt_wire_qname() that returns the
QNAME in the wire format buffer. This is implemented the same as the
original knot_pkt_qname() function before this branch, but now that we
no longer modify the QNAME in the wire format buffer in-place, this
should now be the "original" QNAME as seen off the wire (if the packet
was parsed from a socket buffer).

src/libknot/packet/pkt.h

@@ -188,6 +188,15 @@ static inline const knot_dname_t *knot_pkt_qname(const knot_pkt_t *pkt)
 	return pkt->lower_qname;
 }
 
+static inline const knot_dname_t *knot_pkt_wire_qname(const knot_pkt_t *pkt)
+{
+	if (pkt == NULL || pkt->qname_size == 0) {
+		return NULL;
+	}
+
+	return pkt->wire + KNOT_WIRE_HEADER_SIZE;
+}
+
 static inline uint16_t knot_pkt_qtype(const knot_pkt_t *pkt)
 {
 	if (pkt == NULL || pkt->qname_size == 0) {