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/Makefile b/sigtran/Makefile
new file mode 100644
index 0000000..06a8ba6
--- /dev/null
+++ b/sigtran/Makefile
@@ -0,0 +1,17 @@
+LDADD := -ltalloc -lsctp $(shell pkg-config --libs libosmo-sccp) $(shell pkg-config --libs libosmocore) $(shell pkg-config --libs libosmo-netif)
+LDFLAGS += $(LDADD)
+CFLAGS += -Wall
+
+all: sua_client_test sua_server_test
+
+%.o: %.c
+	$(CC) $(CFLAGS) -o $@ -c $^
+
+sua_client_test: sccp_sap.o sua.o sua_client_test.o sua_test_common.o /usr/local/lib/libxua.a
+	$(CC) $(LDFLAGS) -o $@ $^
+
+sua_server_test: sccp_sap.o sua.o sua_server_test.o sua_test_common.o /usr/local/lib/libxua.a
+	$(CC) $(LDFLAGS) -o $@ $^
+
+clean:
+	@rm *.o sua_client_test sua_server_test