nat: Add MGCP code and parsing to the nat code..

For the nat we will have NAT and MGCP in the same process
and this commit starts with that. We are linking in the MGCP
code and one can embed MGCP config snippets...
diff --git a/openbsc/src/nat/bsc_nat_vty.c b/openbsc/src/nat/bsc_nat_vty.c
index 6dae0d6..3a468e9 100644
--- a/openbsc/src/nat/bsc_nat_vty.c
+++ b/openbsc/src/nat/bsc_nat_vty.c
@@ -25,6 +25,7 @@
 
 #include <openbsc/bsc_nat.h>
 #include <openbsc/gsm_04_08.h>
+#include <openbsc/mgcp.h>
 
 #include <osmocore/talloc.h>
 
@@ -208,6 +209,8 @@
 	install_element(BSC_NODE, &cfg_bsc_token_cmd);
 	install_element(BSC_NODE, &cfg_bsc_lac_cmd);
 
+	mgcp_vty_init();
+
 	return 0;
 }