Using bit record is not a big hit on performance
and may be a winner if there is container
with many children.

GPROF_PROFILING;USE_BIT_RECORD;CPU  ;zmw.so
O6             ;0             ;4.344;176484
O6             ;1             ;4.283;176676
Os             ;0             ;4.706;127428
Os             ;1             ;4.900;129892
               ;0             ;5.729;184368
               ;1             ;6.090;184592






