made some workaround mac-only as apparently other versions of irrlicht don't suffer from this bug

git-svn-id: svn+ssh://svn.code.sf.net/p/supertuxkart/code/main/branches/irrlicht@3427 178a84e3-b1eb-0310-8ba1-8eac791a3b58

src/input/input_manager.cpp

@@ -401,8 +401,10 @@ void InputManager::input(const SEvent& event)
         {
             int value = event.JoystickEvent.Axis[axis_id];
             
+#ifdef __APPLE__
             // work around irrLicht bug. FIXME - get it fixed and remove this
             if(value == -32768) continue; // ignore bogus values given by irrlicht
+#endif
             
             if(user_config->m_gamepad_debug)
             {