Support >INT_MAX -C dirs

* src/extract.c (struct delayed_set_stat, struct delayed_link):
* src/misc.c (normalize_filename, wd_count, chdir_count)
(chdir_arg, tar_getcdpath):
* src/names.c (name_gather, addname, add_hierarchy_to_namelist):
* src/unlink.c (struct deferred_unlink, flush_deferred_unlinks):
Use idx_t, not int, for directory indexes, so as to not
limit their number to INT_MAX; this is theoretically possible
if -T is used.
* src/names.c (name_next_elt, name_next):
Use bool for boolean.

src/create.c

@@ -1395,7 +1395,7 @@ create_archive (void)
   else
     {
       const char *name;
-      while ((name = name_next (1)) != NULL)
+      while ((name = name_next (true)))
 	if (!excluded_name (name, NULL))
 	  dump_file (0, name, name);
     }