osmo_bsc: Use libctrl, handle ctrl cmds on port 4249 or from the nat

This patch initializes libctrl to listen for connections on port 4249.
Additionally, control messages arriving from the nat will also be
processed.
diff --git a/openbsc/src/osmo-bsc/osmo_bsc_main.c b/openbsc/src/osmo-bsc/osmo_bsc_main.c
index 42c74cc..6deed30 100644
--- a/openbsc/src/osmo-bsc/osmo_bsc_main.c
+++ b/openbsc/src/osmo-bsc/osmo_bsc_main.c
@@ -50,6 +50,8 @@
 extern const char *openbsc_copyright;
 static int daemonize = 0;
 
+extern void controlif_setup(struct gsm_network *gsmnet, uint16_t port);
+
 static void print_usage()
 {
 	printf("Usage: osmo-bsc\n");
@@ -204,6 +206,8 @@
 	}
 	bsc_api_init(bsc_gsmnet, osmo_bsc_api());
 
+	controlif_setup(bsc_gsmnet, 4249);
+
 	data = bsc_gsmnet->msc_data;
 	if (rf_ctl)
 		bsc_replace_string(data, &data->rf_ctrl_name, rf_ctl);