Introduce a VTY, factually turning OpenGGSN into an Osmocom program

Change-Id: I9613ca3436e77ea132c47f0096df7c5050d7e826
diff --git a/sgsnemu/sgsnemu.c b/sgsnemu/sgsnemu.c
index 1f0b3f9..ed1fb93 100644
--- a/sgsnemu/sgsnemu.c
+++ b/sgsnemu/sgsnemu.c
@@ -1461,7 +1461,7 @@
 	if (options.createif) {
 		printf("Setting up interface\n");
 		/* Create a tunnel interface */
-		if (tun_new((struct tun_t **)&tun)) {
+		if (tun_new((struct tun_t **)&tun, NULL)) {
 			SYS_ERR(DSGSN, LOGL_ERROR, 0,
 				"Failed to create tun");
 			exit(1);