Do the TCP write in one write

Before the tcp writes were done like NSD does them:
2 bytes length, and the rest of the message.

Now a complete buffer is created with LLMMM...MMM, where
LL is the 2 byte length and MMM...MMM is the message to be send.
This makes the reply faster at the cost of doing a realloc of the
message buffer.

client.go

@@ -253,18 +253,10 @@ func (w *reply) write(p []byte) (n int, err error) {
 		}
 		for a := 0; a < attempts; a++ {
 			setTimeouts(w)
-			a, b := packUint16(uint16(len(p)))
-			n, err = w.conn.Write([]byte{a, b})
-			if err != nil {
-				if e, ok := err.(net.Error); ok && e.Timeout() {
-					continue
-				}
-				return n, err
-			}
-			if n != 2 {
-				return n, io.ErrShortWrite
-			}
-			n, err = w.conn.Write(p)
+			l := make([]byte, 2)
+			l[0], l[1] = packUint16(uint16(len(p)))
+			p = append(l, p...)
+			n, err := w.conn.Write(p)
 			if err != nil {
 				if e, ok := err.(net.Error); ok && e.Timeout() {
 					continue

server.go

@@ -8,7 +8,6 @@ package dns
 
 import (
 	"github.com/miekg/radix"
-	"io"
 	"net"
 	"time"
 )
@@ -425,7 +424,7 @@ func (w *response) Write(m *Msg) (err error) {
 }
 
 // WriteBuf implements the ResponseWriter.WriteBuf method.
-func (w *response) WriteBuf(m []byte) (err error) {
+func (w *response) WriteBuf(m []byte) error {
 	switch {
 	case w._UDP != nil:
 		_, err := w._UDP.WriteTo(m, w.remoteAddr)
@@ -436,15 +435,10 @@ func (w *response) WriteBuf(m []byte) (err error) {
 		if len(m) > MaxMsgSize {
 			return &Error{Err: "message too large"}
 		}
-		a, b := packUint16(uint16(len(m)))
-		n, err := w._TCP.Write([]byte{a, b})
-		if err != nil {
-			return err
-		}
-		if n != 2 {
-			return io.ErrShortWrite
-		}
-		n, err = w._TCP.Write(m)
+		l := make([]byte, 2)
+		l[0], l[1] = packUint16(uint16(len(m)))
+		m = append(l, m...)
+		n, err := w._TCP.Write(m)
 		if err != nil {
 			return err
 		}

zone.go

@@ -16,7 +16,7 @@ import (
 // multilpe goroutines.
 type Zone struct {
 	Origin       string   // Origin of the zone
-	olabels      []string // origin cut up in labels, to speed up IsSubDomain function
+	olabels      []string // origin cut up in labels, just to speed up the isSubDomain method
 	Wildcard     int      // Whenever we see a wildcard name, this is incremented
 	*radix.Radix          // Zone data
 	mutex        *sync.RWMutex