Pull request: 3444 reuse port

Merge in DNS/adguard-home from 3444-dhcp-again to master

Closes #3444.

Squashed commit of the following:

commit 5459ded7d58f219ab5417977e0df17c177c73a4a
Merge: d6559090 8e667d3c
Author: Eugene Burkov <e.burkov@adguard.com>
Date:   Mon Aug 16 15:35:30 2021 +0300

    Merge branch 'master' into 3444-dhcp-again

commit d6559090a21b6b13be6970a3839db1106fb539b8
Author: Eugene Burkov <e.burkov@adguard.com>
Date:   Mon Aug 16 15:28:38 2021 +0300

    aghnet: fix linux

commit 262f729224d73a70d61a4b29d5a4d34502b7b094
Author: Eugene Burkov <e.burkov@adguard.com>
Date:   Mon Aug 16 14:30:09 2021 +0300

    aghnet: rm debug

commit c54b107264f792ec7f17f8d790908408070307d3
Author: Eugene Burkov <e.burkov@adguard.com>
Date:   Mon Aug 16 14:21:07 2021 +0300

    aghnet: imp bsd compat, fix openbsd static ip

commit f9871a4c51d1f5d2c799a8d1308a4d30a47485f6
Author: Eugene Burkov <e.burkov@adguard.com>
Date:   Sat Aug 14 00:17:46 2021 +0300

    aghnet:  setsockopt

internal/aghnet/interfaces_windows.go

@@ -0,0 +1,18 @@
+//go:build windows
+// +build windows
+
+package aghnet
+
+import (
+	"net"
+
+	"github.com/AdguardTeam/AdGuardHome/internal/aghos"
+)
+
+// listenPacketReusable announces on the local network address additionally
+// configuring the socket to have a reusable binding.
+func listenPacketReusable(_, _, _ string) (c net.PacketConn, err error) {
+	// TODO(e.burkov):  Check if we are able to control sockets on Windows
+	// in the same way as on Unix.
+	return nil, aghos.Unsupported("listening packet reusable")
+}