GCS_MAVLink: add AC_POLYFENCE_CIRCLE_INT_SUPPORT_ENABLED

... and a plan to get rid of this compatability code

Author: peterbarker

libraries/GCS_MAVLink/MissionItemProtocol_Fence.cpp

@@ -52,11 +52,13 @@ bool MissionItemProtocol_Fence::get_item_as_mission_item(uint16_t seq,
         ret_cmd = MAV_CMD_NAV_FENCE_CIRCLE_INCLUSION;
         p1 = fenceitem.radius;
         break;
+#if AC_POLYFENCE_CIRCLE_INT_SUPPORT_ENABLED
     case AC_PolyFenceType::CIRCLE_EXCLUSION_INT:
     case AC_PolyFenceType::CIRCLE_INCLUSION_INT:
         // should never have an AC_PolyFenceItem with these types
         INTERNAL_ERROR(AP_InternalError::error_t::flow_of_control);
         FALLTHROUGH;
+#endif  // AC_POLYFENCE_CIRCLE_INT_SUPPORT_ENABLED
     case AC_PolyFenceType::END_OF_STORAGE:
         return false;
     }