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/Makefile.am b/src/libmsc/Makefile.am
index 9f246b3..c9b8bb4 100644
--- a/src/libmsc/Makefile.am
+++ b/src/libmsc/Makefile.am
@@ -35,8 +35,6 @@
 	gsm_04_14.c \
 	gsm_04_80.c \
 	gsm_subscriber.c \
-	iucs.c \
-	iucs_ranap.c \
 	mncc.c \
 	mncc_builtin.c \
 	mncc_sock.c \
@@ -52,7 +50,12 @@
 	meas_feed.c \
 	subscr_conn.c \
 	$(NULL)
-if !BUILD_IU
+if BUILD_IU
+libmsc_a_SOURCES += \
+	iucs.c \
+	iucs_ranap.c \
+	$(NULL)
+else
 libmsc_a_SOURCES += \
 	iu_dummy.c \
 	$(NULL)