Add option to ignore special files.

demo/iso.c

@@ -130,6 +130,7 @@ int main(int argc, char **argv)
     iso_image_set_msgs_severities(image, "NEVER", "ALL", "");
     iso_tree_set_follow_symlinks(image, 0);
     iso_tree_set_ignore_hidden(image, 0);
+    iso_tree_set_ignore_special(image, 0);
     iso_tree_set_stop_on_error(image, 0);
     
     result = iso_tree_add_dir_rec(image, iso_image_get_root(image), argv[optind]);