Add WIP code for SCCP User Adaptation (SUA) and SCCP User SAP

The idea of this code is to
* provide a SCCP User SAP as boundary between the User of SCCP
  or SCCP-like transport like SUA
* implement the minimum subset of SUA to transport RANAP messages
  betweene HNB-GW and MSC/SGSN

At this point
* we don't yet implement the proper state machines and timer
* we don't imp[lement the SCCP RESET procedure
* we don't implement AS/ASP management

The code is full of FIXMEs whihc hopefully will get fixed gradually.

After some cleanup + verification, it should move to a library, possibly
either replacing/renaming libomo-sccp, or adding it to libosmo-netif?
diff --git a/sigtran/proto_sua.h b/sigtran/proto_sua.h
new file mode 100644
index 0000000..4b97d9f
--- /dev/null
+++ b/sigtran/proto_sua.h
@@ -0,0 +1,122 @@
+/* RFC 3868 SUA SCCP User Adaption */
+
+/* (C) 2012 by Harald Welte <laforge@gnumonks.org>
+ %
+ % All Rights Reserved
+ %
+ % This program is free software; you can redistribute it and/or modify
+ % it under the terms of the GNU Affero General Public License as
+ % published by the Free Software Foundation; either version 3 of the
+ % License, or (at your option) any later version.
+ %
+ % This program is distributed in the hope that it will be useful,
+ % but WITHOUT ANY WARRANTY; without even the implied warranty of
+ % MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ % GNU General Public License for more details.
+ %
+ % You should have received a copy of the GNU Affero General Public License
+ % along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+#include <stdint.h>
+
+//#include <osmocom/ss7/xua.h>
+
+#define SUA_PPID	4
+#define SUA_PORT 	14001
+
+/* 3.1.2 Message Classes */
+#define SUA_MSGC_MGMT	0
+#define SUA_MSGC_SNM	2
+#define SUA_MSGC_ASPSM	3
+#define SUA_MSGC_ASPTM	4
+#define SUA_MSGC_CL	7
+#define SUA_MSGC_CO	8
+#define SUA_MSGC_RKM	9
+
+/* 3.1.3 Message Types */
+#define SUA_MGMT_ERR	0
+#define SUA_MGMT_NTFY	1
+
+#define SUA_SNM_DUNA	1
+#define SUA_SNM_DAVA	2
+#define SUA_SNM_DAUD	3
+#define SUA_SNM_SCON	4
+#define SUA_SNM_DUPU	5
+#define SUA_SNM_DRST	6
+
+#define SUA_ASPSM_UP		1
+#define SUA_ASPSM_DOWN		2
+#define SUA_ASPSM_BEAT		3
+#define SUA_ASPSM_UP_ACK 	4
+#define SUA_ASPSM_DOWN_ACK	5
+#define SUA_ASPSM_BEAT_ACK	6
+
+#define SUA_ASPTM_ACTIVE	1
+#define SUA_ASPTM_INACTIVE	2
+#define SUA_ASPTM_ACTIVE_ACK	3
+#define SUA_ASPTM_INACTIVE_ACK	4
+
+#define SUA_RKM_REG_REQ		1
+#define SUA_RKM_REG_RSP		2
+#define SUA_RKM_DEREG_REQ	3
+#define SUA_RKM_DEREG_RSP	4
+
+#define SUA_CL_CLDT	 	1
+#define SUA_CL_CLDR	 	2
+
+#define SUA_CO_CORE		1
+#define SUA_CO_COAK		2
+#define SUA_CO_COREF		3
+#define SUA_CO_RELRE		4
+#define SUA_CO_RELCO		5
+#define SUA_CO_RESCO		6
+#define SUA_CO_RESRE		7
+#define SUA_CO_CODT		8
+#define SUA_CO_CODA		9
+#define SUA_CO_COERR		10
+#define SUA_CO_COIT		11
+
+#define SUA_IEI_ROUTE_CTX	0x0006
+#define SUA_IEI_CORR_ID		0x0013
+#define SUA_IEI_REG_RESULT	0x0014
+#define SUA_IEI_DEREG_RESULT	0x0015
+
+/* 3.10 SUA specific parameters */
+
+#define SUA_IEI_S7_HOP_CTR	0x0101
+#define SUA_IEI_SRC_ADDR	0x0102
+#define SUA_IEI_DEST_ADDR	0x0103
+#define SUA_IEI_SRC_REF		0x0104
+#define SUA_IEI_DEST_REF	0x0105
+#define SUA_IEI_CAUSE		0x0106
+#define SUA_IEI_SEQ_NR		0x0107
+#define SUA_IEI_RX_SEQ_NR	0x0108
+#define SUA_IEI_ASP_CAPA	0x0109
+#define SUA_IEI_CREDIT		0x010A
+#define SUA_IEI_DATA		0x010B
+#define SUA_IEI_USER_CAUSE	0x010C
+#define SUA_IEI_NET_APPEARANCE	0x010D
+#define SUA_IEI_ROUTING_KEY	0x010E
+#define SUA_IEI_DRN		0x010F
+#define SUA_IEI_TID		0x0110
+#define SUA_IEI_SMI		0x0112
+#define SUA_IEI_IMPORTANCE	0x0113
+#define SUA_IEI_MSG_PRIO	0x0114
+#define SUA_IEI_PROTO_CLASS	0x0115
+#define SUA_IEI_SEQ_CTRL	0x0116
+#define SUA_IEI_SEGMENTATION	0x0117
+#define SUA_IEI_CONG_LEVEL	0x0118
+
+#define SUA_IEI_GT	0x8001
+#define SUA_IEI_PC	0x8002
+#define SUA_IEI_SSN	0x8003
+#define SUA_IEI_IPv4	0x8004
+#define SUA_IEI_HOST	0x8005
+#define SUA_IEI_IPv6	0x8006
+
+#define SUA_RI_GT	1
+#define SUA_RI_SSN_PC	2
+#define SUA_RI_HOST	3
+#define SUA_RI_SSN_IP	4