Allocate just enough space

Remove the len()*2, and replace it with len()+1. The current
len() impl. of the types is good enough to be more precise.

dnssec.go

@@ -685,7 +685,7 @@ func rawSignatureData(rrset []RR, s *RRSIG) (buf []byte, err error) {
 			x.Target = strings.ToLower(x.Target)
 		}
 		// 6.2. Canonical RR Form. (5) - origTTL
-		wire := make([]byte, r1.len()*2) // TODO(mg): *2 ?
+		wire := make([]byte, r1.len()+1) // +1 to be safe(r)
 		off, err1 := PackRR(r1, wire, 0, nil, false)
 		if err1 != nil {
 			return nil, err1

types.go

@@ -1181,7 +1181,7 @@ func (rr *TKEY) len() int {
 		len(rr.Key) + 2 + len(rr.OtherData)
 }
 
-// RFC3597 representes an unknown/generic RR.
+// RFC3597 represents an unknown/generic RR.
 type RFC3597 struct {
 	Hdr   RR_Header
 	Rdata string `dns:"hex"`