default-FOO variables

[Eli Zaretskii]

What does this entry in NEWS:

   ** All the default-FOO variables that hold the default value of the FOO
   variable, are now declared obsolete.

mean for variable declaration in C such as this:

     DEFVAR_LISP_NOPRO ("default-enable-multibyte-characters",
                        &buffer_defaults.enable_multibyte_characters,
                        doc: /* *Default value of `enable-multibyte-characters' 
for buffers not overriding it.
   This is the same as (default-value 'enable-multibyte-characters).  */);

Do we need to avoid such declarations?  If so, how to do the
equivalent of that for buffer-local variables defined in C?