ipfw_objhash_bitmap_alloc
void ipfw_objhash_bitmap_alloc(uint32_t items, void **idx, int *pblocks);
ipfw_objhash_bitmap_alloc(items, (void*)&ni->idx_mask, &ni->max_blocks);
ipfw_objhash_bitmap_alloc(ntables, (void *)&new_idx, &new_blocks);
ipfw_objhash_bitmap_alloc(val_size, (void *)&new_idx,