The decc$feature_show_all function displays to stdout all values
    for all feature names.

    On error, -1 is returned and errno is set to indicate the error.

    See also decc$feature_get, decc$feature_get_index, decc$feature_
    get_name, decc$feature_get_value, decc$feature_set, decc$feature_
    set_value, and decc$feature_show.