reserved config numbers in ndb

#define CFG_DB_BACKUP_DATADIR         158

#define CFG_DB_MAX_OPEN_FILES         159

#define CFG_DB_DISK_PAGE_BUFFER_MEMORY 160 /* used from 5.1 */

#define CFG_DB_STRING_MEMORY          161 /* used from 5.1 */

#define CFG_DB_INITIAL_OPEN_FILES     162 /* used from 5.1 */

#define CFG_DB_DATA_MEM_2             199 /* used in special build in 5.1 */

#define CFG_NODE_ARBIT_RANK           200

#define CFG_NODE_ARBIT_DELAY          201