Deleting from an RTRB Tree - GNU libavl 2.0.2

The process of deletion from an RTRB tree is the same that we've seen many times now. Code for the first step is borrowed from RTAVL deletion:

468. <RTRB item deletion function 468> =
void *
rtrb_delete (struct rtrb_table *tree, const void *item) 
{
  struct rtrb_node *pa[RTRB_MAX_HEIGHT]; /* Nodes on stack. */
  unsigned char da[RTRB_MAX_HEIGHT];   /* Directions moved from stack nodes. */
  int k;                               /* Stack height. */

  struct rtrb_node *p;

  assert (tree != NULL && item != NULL);

  <Step 1: Search RTAVL tree for item to delete; rtavl => rtrb 430>
  <Step 2: Delete RTRB node 469>
  <Step 3: Rebalance after RTRB deletion 474>
  <Step 4: Finish up after RTRB deletion 481>
}

This code is included in 455.