Once you are done with the string arrays filled in by list_config_entries and
list_config_sections, you can free them again with this function. The passed
array pointer will be set to NULL, and you directly can pass the same pointer
again to list_config_entries or list_config_sections later - but you also
could pass them again without freeing first, since the memory is re-allocated
when the pointer is not NULL.
See list_config_entries for an example of how to use it.