Add app source, add vendoring and module support

vendor/github.com/vishvananda/netlink/link_tuntap_linux.go

@@ -0,0 +1,14 @@
+package netlink
+
+// ideally golang.org/x/sys/unix would define IfReq but it only has
+// IFNAMSIZ, hence this minimalistic implementation
+const (
+	SizeOfIfReq = 40
+	IFNAMSIZ    = 16
+)
+
+type ifReq struct {
+	Name  [IFNAMSIZ]byte
+	Flags uint16
+	pad   [SizeOfIfReq - IFNAMSIZ - 2]byte
+}