BZ_N_OVERSHOOT
if (a2update < BZ_N_OVERSHOOT)
i = nblock+BZ_N_OVERSHOOT;
for (i = 0; i < BZ_N_OVERSHOOT; i++) {
s->arr2 = BZALLOC( (n+BZ_N_OVERSHOOT) * sizeof(UInt32) );
t += ( (n+BZ_N_OVERSHOOT) * sizeof(UInt32) );