message: mission: fix VS2016 x64 Native Tools warnings
diff: @@ -245,7 +245,8 @@ void MissionImpl::assemble_mavlink_messages()
  MAV_MISSION_TYPE_MISSION);
  _mavlink_mission_item_to_mission_item_indices.insert(
  - std::pair <int, int> {_mavlink_mission_item_messages.size(), item_i});
  + std::pair <int, int>
  + {static_cast<int>(_mavlink_mission_item_messages.size()), item_i});
  _mavlink_mission_item_messages.push_back(message);
  }
  @@ -280,7 +281,8 @@ void MissionImpl::assemble_mavlink_messages()
  MAV_MISSION_TYPE_MISSION);
  _mavlink_mission_item_to_mission_item_indices.insert(
  - std::pair <int, int> {_mavlink_mission_item_messages.size(), item_i});
  + std::pair <int, int>
  + {static_cast<int>(_mavlink_mission_item_messages.size()), item_i});
  _mavlink_mission_item_messages.push_back(message_speed);
  last_speed_m_s = mission_item_impl.get_speed_m_s();
  @@ -318,7 +320,8 @@ void MissionImpl::assemble_mavlink_messages()
  MAV_MISSION_TYPE_MISSION);
  _mavlink_mission_item_to_mission_item_indices.insert(
  - std::pair <int, int> {_mavlink_mission_item_messages.size(), item_i});
  + std::pair <int, int>
  + {static_cast<int>(_mavlink_mission_item_messages.size()), item_i});
  _mavlink_mission_item_messages.push_back(message_gimbal);
  last_gimbal_yaw_deg = mission_item_impl.get_gimbal_yaw_deg();
  @@ -388,7 +391,8 @@ void MissionImpl::assemble_mavlink_messages()
  MAV_MISSION_TYPE_MISSION);
  _mavlink_mission_item_to_mission_item_indices.insert(
  - std::pair <int, int> {_mavlink_mission_item_messages.size(), item_i});
  + std::pair <int, int>
  + {static_cast<int>(_mavlink_mission_item_messages.size()), item_i});
  _mavlink_mission_item_messages.push_back(message_camera);
  last_gimbal_yaw_deg = mission_item_impl.get_gimbal_yaw_deg();
  