RB_TREE_NEXT
tchunk = RB_TREE_NEXT(&old_chunks, delchunk);
tchunk = RB_TREE_NEXT(&old_chunks, delchunk);
pve = RB_TREE_NEXT(tree, pve);
i++, sc0 = RB_TREE_NEXT(&ugenif.tree, sc0))
for ((N) = RB_TREE_MIN(T); (N); (N) = RB_TREE_NEXT((T), (N)))
(N) && ((S) = RB_TREE_NEXT((T), (N)), 1); \