TUN-1615: revert miekg/dns to last known working revision

The last known good commit is 6da3249dfb57fbaa16efafcd8744cee8809d80cd before the first release tag.

vendor/golang.org/x/net/ipv6/payload_cmsg.go

@@ -1,32 +0,0 @@
-// Copyright 2013 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-// +build !nacl,!plan9,!windows
-
-package ipv6
-
-import "net"
-
-// ReadFrom reads a payload of the received IPv6 datagram, from the
-// endpoint c, copying the payload into b. It returns the number of
-// bytes copied into b, the control message cm and the source address
-// src of the received datagram.
-func (c *payloadHandler) ReadFrom(b []byte) (n int, cm *ControlMessage, src net.Addr, err error) {
-	if !c.ok() {
-		return 0, nil, nil, errInvalidConn
-	}
-	return c.readFrom(b)
-}
-
-// WriteTo writes a payload of the IPv6 datagram, to the destination
-// address dst through the endpoint c, copying the payload from b. It
-// returns the number of bytes written. The control message cm allows
-// the IPv6 header fields and the datagram path to be specified. The
-// cm may be nil if control of the outgoing datagram is not required.
-func (c *payloadHandler) WriteTo(b []byte, cm *ControlMessage, dst net.Addr) (n int, err error) {
-	if !c.ok() {
-		return 0, errInvalidConn
-	}
-	return c.writeTo(b, cm, dst)
-}