2.6.10 File Label
A dictionary may optionally have an associated string that describes
its contents, called its file label. The user may set the file label
with the FILE LABEL command (see FILE LABEL).
These functions set and retrieve the file label.
— Function: const char * dict_get_label
(const struct dictionary *dict
Returns dict's file label. If dict does not have a label,
returns a null pointer.
— Function: void dict_set_label
(struct dictionary *dict, const char *label
Sets dict's label to label. If label is non-null,
then its content, truncated to at most 60 bytes, becomes the new file
label. If label is null, then dict's label is removed.
The caller retains ownership of label.