[sccp] Parse the error message and add a unit test for it.
diff --git a/openbsc/include/sccp/sccp_types.h b/openbsc/include/sccp/sccp_types.h
index 42fda96..22bd70f 100644
--- a/openbsc/include/sccp/sccp_types.h
+++ b/openbsc/include/sccp/sccp_types.h
@@ -411,4 +411,10 @@
 	u_int8_t			credit;
 } __attribute__((packed));
 
+struct sccp_proto_err {
+	u_int8_t			type;
+	struct sccp_source_reference	destination_local_reference;
+	u_int8_t			error_cause;
+};
+
 #endif