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/ipv4/sockopt.go

@@ -1,44 +0,0 @@
-// Copyright 2014 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.
-
-package ipv4
-
-import "golang.org/x/net/internal/socket"
-
-// Sticky socket options
-const (
-	ssoTOS                = iota // header field for unicast packet
-	ssoTTL                       // header field for unicast packet
-	ssoMulticastTTL              // header field for multicast packet
-	ssoMulticastInterface        // outbound interface for multicast packet
-	ssoMulticastLoopback         // loopback for multicast packet
-	ssoReceiveTTL                // header field on received packet
-	ssoReceiveDst                // header field on received packet
-	ssoReceiveInterface          // inbound interface on received packet
-	ssoPacketInfo                // incbound or outbound packet path
-	ssoHeaderPrepend             // ipv4 header prepend
-	ssoStripHeader               // strip ipv4 header
-	ssoICMPFilter                // icmp filter
-	ssoJoinGroup                 // any-source multicast
-	ssoLeaveGroup                // any-source multicast
-	ssoJoinSourceGroup           // source-specific multicast
-	ssoLeaveSourceGroup          // source-specific multicast
-	ssoBlockSourceGroup          // any-source or source-specific multicast
-	ssoUnblockSourceGroup        // any-source or source-specific multicast
-	ssoAttachFilter              // attach BPF for filtering inbound traffic
-)
-
-// Sticky socket option value types
-const (
-	ssoTypeIPMreq = iota + 1
-	ssoTypeIPMreqn
-	ssoTypeGroupReq
-	ssoTypeGroupSourceReq
-)
-
-// A sockOpt represents a binding for sticky socket option.
-type sockOpt struct {
-	socket.Option
-	typ int // hint for option value type; optional
-}