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-util.c

@@ -187,6 +187,11 @@ ctf_next_create (void)
 void
 ctf_next_destroy (ctf_next_t *i)
 {
+  if (i == NULL)
+    return;
+
+  if (i->ctn_iter_fun == (void (*) (void)) ctf_dynhash_next_sorted)
+    free (i->u.ctn_sorted_hkv);
   free (i);
 }
 
@@ -200,5 +205,17 @@ ctf_next_copy (ctf_next_t *i)
   if ((i2 = ctf_next_create()) == NULL)
     return NULL;
   memcpy (i2, i, sizeof (struct ctf_next));
+
+  if (i2->ctn_iter_fun == (void (*) (void)) ctf_dynhash_next_sorted)
+    {
+      size_t els = ctf_dynhash_elements ((ctf_dynhash_t *) i->cu.ctn_h);
+      if ((i2->u.ctn_sorted_hkv = calloc (els, sizeof (ctf_next_hkv_t))) == NULL)
+	{
+	  free (i2);
+	  return NULL;
+	}
+      memcpy (i2->u.ctn_sorted_hkv, i->u.ctn_sorted_hkv,
+	      els * sizeof (ctf_next_hkv_t));
+    }
   return i2;
 }