e two children differ by at most 1.
In addition, check that the inorder traversal of the whole
tree really is in order.
<A NAME="avl_delete"></A><HR><PRE><B>Avl_node avl_delete(Avl_node p, void *item,
		    Ordertype (*compare) (void *, void *));
</B></PRE>Delete an item from an AVL tree and return the updated tree.
If the item is not in the tree (that is, if the comparison
function does not return SAME_AS for any item in the tree),
a fatal error occurs.
<A NAME="avl_find"></A><HR><PRE><B>void *avl_find(Avl