nat: Move SCCP patching to a new file, log updates

Move patching and reassigning of messages to a new file which
will making testing this functionality more easy.
diff --git a/openbsc/include/openbsc/bsc_nat.h b/openbsc/include/openbsc/bsc_nat.h
index 5ac60df..9aa9948 100644
--- a/openbsc/include/openbsc/bsc_nat.h
+++ b/openbsc/include/openbsc/bsc_nat.h
@@ -148,4 +148,12 @@
 int bsc_nat_filter_ipa(int direction, struct msgb *msg, struct bsc_nat_parsed *parsed);
 int bsc_nat_vty_init(struct bsc_nat *nat);
 
+/**
+ * SCCP patching and handling
+ */
+int create_sccp_src_ref(struct bsc_connection *bsc, struct msgb *msg, struct bsc_nat_parsed *parsed);
+void remove_sccp_src_ref(struct bsc_connection *bsc, struct msgb *msg, struct bsc_nat_parsed *parsed);
+struct bsc_connection *patch_sccp_src_ref_to_bsc(struct msgb *, struct bsc_nat_parsed *, struct bsc_nat *);
+struct bsc_connection *patch_sccp_src_ref_to_msc(struct msgb *, struct bsc_nat_parsed *, struct bsc_nat *);
+
 #endif