bts: Move struct gprs_rlcmac_bts and other structs into a bts.h

Begin to make the BTS a real C++ object with real responsibilities.
The biggest issue will be the pcu_vty.c that might not like C++
at all.
diff --git a/src/tbf.cpp b/src/tbf.cpp
index 3f6b92f..2753260 100644
--- a/src/tbf.cpp
+++ b/src/tbf.cpp
@@ -19,6 +19,7 @@
  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
  */
 
+#include <bts.h>
 #include <tbf.h>
 #include <gprs_rlcmac.h>
 #include <gprs_debug.h>