more logical table/index_flags
  return  HA_ERR_WRONG_COMMAND instead of abstract methods where appropriate
  max_keys and other limits renamed to max_supported_keys/etc
  max_keys/etc are now wrappers to max_supported_keys/etc 
  ha_index_init/ha_rnd_init/ha_index_end/ha_rnd_end are now wrappers to real {index,rnd}_{init,end} to enforce strict pairing