AP_HAL: use variadic templates in FastDelegate

Now that we are using C++11 we can use variadic templates to simplify
the FastDelegate classes. It also simplifies moving away from the
FastDelegate implementation.

libraries/AP_HAL/AP_HAL_Namespace.h

@@ -24,8 +24,10 @@
 #define AP_HAL_MEMBERPROC(func) AP_HAL_CLASSPROC(this, func)
 
 #define DELEGATE_FUNCTION0(rettype)          fastdelegate::FastDelegate0<rettype>
-#define DELEGATE_FUNCTION1(rettype, args...) fastdelegate::FastDelegate1<args, rettype>
-#define DELEGATE_FUNCTION2(rettype, args...) fastdelegate::FastDelegate2<args, rettype>
+#define DELEGATE_FUNCTION1(rettype, args...) fastdelegate::FastDelegate0<rettype, args>
+#define DELEGATE_FUNCTION2(rettype, args...) fastdelegate::FastDelegate0<rettype, args>
+
+#define DELEGATE_FUNCTION(rettype, ...) fastdelegate::FastDelegate0<rettype, ## __VA_ARGS__>
 
 #ifndef APM_BUILD_FUNCTOR
 #define APM_BUILD_FUNCTOR 0