libctf, next, hash: add dynhash and dynset _next iteration

This lets you iterate over dynhashes and dynsets using the _next API.
dynhashes can be iterated over in sorted order, which works by
populating an array of key/value pairs using ctf_dynhash_next itself,
then sorting it with qsort.

Convenience inline functions named ctf_dyn{hash,set}_cnext are also
provided that take (-> return) const keys and values.

libctf/
	* ctf-impl.h (ctf_next_hkv_t): New, kv-pairs passed to
	sorting functions.
	(ctf_next_t) <u.ctn_sorted_hkv>: New, sorted kv-pairs for
	ctf_dynhash_next_sorted.
	<cu.ctn_h>: New, pointer to the dynhash under iteration.
	<cu.ctn_s>: New, pointer to the dynset under iteration.
	(ctf_hash_sort_f): Sorting function passed to...
	(ctf_dynhash_next_sorted): ... this new function.
	(ctf_dynhash_next): New.
	(ctf_dynset_next): New.
	* ctf-inlines.h (ctf_dynhash_cnext_sorted): New.
	(ctf_dynhash_cnext): New.
	(ctf_dynset_cnext): New.
	* ctf-hash.c (ctf_dynhash_next_sorted): New.
	(ctf_dynhash_next): New.
	(ctf_dynset_next): New.
	* ctf-util.c (ctf_next_destroy): Free the u.ctn_sorted_hkv if
	needed.
	(ctf_next_copy): Alloc-and-copy the u.ctn_sorted_hkv if needed.

libctf/ctf-inlines.h

@@ -46,6 +46,21 @@ ctf_forwardable_kind (int kind)
   return (kind == CTF_K_STRUCT || kind == CTF_K_UNION || kind == CTF_K_ENUM);
 }
 
+static inline int
+ctf_dynhash_cnext_sorted (ctf_dynhash_t *h, ctf_next_t **i, const void **key,
+			  const void **value, ctf_hash_sort_f sort_fun,
+			  void *sort_arg)
+{
+  return ctf_dynhash_next_sorted (h, i, (void **) key, (void **) value,
+				  sort_fun, sort_arg);
+}
+
+static inline int
+ctf_dynhash_cnext (ctf_dynhash_t *h, ctf_next_t **it,
+		  const void **key, const void **value)
+{
+  return ctf_dynhash_next (h, it, (void **) key, (void **) value);
+}
 
 static inline int
 ctf_dynhash_cinsert (ctf_dynhash_t *h, const void *k, const void *v)
@@ -53,6 +68,12 @@ ctf_dynhash_cinsert (ctf_dynhash_t *h, const void *k, const void *v)
   return ctf_dynhash_insert (h, (void *) k, (void *) v);
 }
 
+static inline int
+ctf_dynset_cnext (ctf_dynset_t *h, ctf_next_t **it, const void **key)
+{
+  return ctf_dynset_next (h, it, (void **) key);
+}
+
 static inline int
 ctf_dynset_cinsert (ctf_dynset_t *h, const void *k)
 {