move libiu to osmo-iuh/libosmo-ranap

Remove libiu here, use the functions from libosmo-ranap instead, by applying
the ranap_ / RANAP_ prefix.

Corresponding change-id in osmo-iuh.git is I6a3f7ad15be03fb94689b4af6ccfa828c25f45c0

To be able to run the msc_vlr tests for RAN_UTRAN_IU without Iu client headers
available, add iu_dummy.h, containing mere function signatures that match
iu_dummy.c and a mostly empty struct ranap_ue_conn_ctx.

Make sure we can build with and without --enable-iu: include osmo-iuh headers
only with --enable-iu.

Change-Id: Ib8c4fcdb4766c5e575618b95ce16dce51063206b
diff --git a/src/libmsc/gsm_04_08.c b/src/libmsc/gsm_04_08.c
index b6746a5..21bc2b8 100644
--- a/src/libmsc/gsm_04_08.c
+++ b/src/libmsc/gsm_04_08.c
@@ -72,13 +72,11 @@
 #include <osmocom/core/utils.h>
 #include <osmocom/gsm/tlv.h>
 #include <osmocom/crypt/auth.h>
-
-#include <openbsc/msc_ifaces.h>
-
 #ifdef BUILD_IU
-#include <openbsc/iu.h>
+#include <osmocom/ranap/iu_client.h>
 #endif
 
+#include <openbsc/msc_ifaces.h>
 #include <openbsc/a_iface.h>
 
 #include <assert.h>
@@ -3412,7 +3410,7 @@
 #ifdef BUILD_IU
 		DEBUGP(DMM, "-> SECURITY MODE CONTROL %s\n",
 		       vlr_subscr_name(conn->vsub));
-		return iu_tx_sec_mode_cmd(conn->iu.ue_ctx, tuple, 0, 1);
+		return ranap_iu_tx_sec_mode_cmd(conn->iu.ue_ctx, &tuple->vec, 0, 1);
 #else
 		LOGP(DMM, LOGL_ERROR, "Cannot send Security Mode Control over RAN_UTRAN_IU,"
 		     " built without Iu support\n");