Implement IuCS (large refactoring and addition)

osmo-nitb becomes osmo-msc
add DIUCS debug log constant
add iucs.[hc]
add msc vty, remove nitb vty
add libiudummy, to avoid linking Iu deps in tests
Use new msc_tx_dtap() instead of gsm0808_submit_dtap()
libmgcp: add mgcpgw client API
bridge calls via mgcpgw

Enable MSC specific CTRL commands, bsc_base_ctrl_cmds_install() still needs to
be split up.

Change-Id: I5b5b6a9678b458affa86800afb1ec726e66eed88
diff --git a/src/libbsc/paging.c b/src/libbsc/paging.c
index 8c1445c..e19c2d1 100644
--- a/src/libbsc/paging.c
+++ b/src/libbsc/paging.c
@@ -57,6 +57,12 @@
 #define PAGING_TIMER 0, 500000
 
 /*
+ * TODO MSCSPLIT: the paging in libbsc is closely tied to MSC land in that the
+ * MSC realm callback functions used to be invoked from the BSC/BTS level. So
+ * this entire file needs to be rewired for use with an A interface.
+ */
+
+/*
  * Kill one paging request update the internal list...
  */
 static void paging_remove_request(struct gsm_bts_paging_state *paging_bts,