Remove empty AP_Var_menufuncs.cpp

libraries/AP_Common/AP_Var_menufuncs.cpp

@@ -1,15 +0,0 @@
-// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
-//
-// This is free software; you can redistribute it and/or modify it under
-// the terms of the GNU Lesser General Public License as published by the
-// Free Software Foundation; either version 2.1 of the License, or (at
-// your option) any later version.
-//
-
-/// @file   AP_Var_menufuncs.cpp
-/// @brief  Useful functions compatible with the menu system for
-///         managing AP_Var variables.
-
-#include <FastSerial.h>
-#include <AP_Common.h>
-