Displays all feature values for all feature names.
    Format
      #include  <unixlib.h>
      int decc$feature_show_all  (void);
1 – Description
    The decc$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.
2 – Return Values
    0                  Indicates success.
    -1                 Indicates an error; errno is set.