posix_tnode
extern void *tdelete(const void *key, posix_tnode **_root,
extern posix_tnode *tfind(const void *key, posix_tnode *const *root,
extern posix_tnode *tsearch(const void *key, posix_tnode **_root,
extern void twalk(const posix_tnode *root,
void (*action)(const posix_tnode *, VISIT, int));