bts/tbf: Move the lists into the BTS and do the look-up from the BTS

The list belongs to the BTS. This makes cleaning this up more easy
and establishes a hierachy of resources that start from the BTS. The
debug_diagram code is now broken.
diff --git a/src/sysmo_sock.cpp b/src/sysmo_sock.cpp
index 6af2e9a..2e2d9d3 100644
--- a/src/sysmo_sock.cpp
+++ b/src/sysmo_sock.cpp
@@ -36,6 +36,7 @@
 #include <gprs_debug.h>
 #include <gprs_bssgp_pcu.h>
 #include <pcuif_proto.h>
+#include <bts.h>
 #include <tbf.h>
 
 extern void *tall_pcu_ctx;