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/tests/mgcp/mgcpgw_client_test.err b/tests/mgcp/mgcpgw_client_test.err
new file mode 100644
index 0000000..a965a70
--- /dev/null
+++ b/tests/mgcp/mgcpgw_client_test.err
@@ -0,0 +1 @@
+Done