Implement AoIP, port to M3UA SIGTRAN (large addition and refactoring)

This was originally a long series of commits converging to the final result
seen in this patch. It does not make much sense to review the smaller steps'
trial and error, we need to review this entire change as a whole.

Implement AoIP in osmo-msc and osmo-bsc.

Change over to the new libosmo-sigtran API with support for proper
SCCP/M3UA/SCTP stacking, as mandated by 3GPP specifications for the IuCS and
IuPS interfaces.

From here on, a separate osmo-stp process is required for SCCP routing between
OsmoBSC / OsmoHNBGW <-> OsmoMSC / OsmoSGSN

jenkins.sh: build from libosmo-sccp and osmo-iuh master branches now for new
M3UA SIGTRAN.

Patch-by: pmaier, nhofmeyr, laforge
Change-Id: I5ae4e05ee7c57cad341ea5e86af37c1f6b0ffa77
diff --git a/src/libmsc/gsm_subscriber.c b/src/libmsc/gsm_subscriber.c
index ac6c96a..73361a1 100644
--- a/src/libmsc/gsm_subscriber.c
+++ b/src/libmsc/gsm_subscriber.c
@@ -43,6 +43,7 @@
 #include <openbsc/iu.h>
 #include <openbsc/osmo_msc.h>
 #include <openbsc/msc_ifaces.h>
+#include <openbsc/a_iface.h>
 
 int subscr_paging_dispatch(unsigned int hooknum, unsigned int event,
 			   struct msgb *msg, void *data, void *param)
@@ -105,7 +106,7 @@
 	 * Need to add BSC paging at some point. */
 	switch (vsub->cs.attached_via_ran) {
 	case RAN_GERAN_A:
-		return a_page(vsub->imsi, vsub->tmsi, vsub->lac);
+		return a_iface_tx_paging(vsub->imsi, vsub->tmsi, vsub->lac);
 	case RAN_UTRAN_IU:
 		return iu_page_cs(vsub->imsi,
 				  vsub->tmsi == GSM_RESERVED_TMSI?