Incompatible Fsubr for SETF

[JONL at MIT-MC (Jon L White)]

For the record, there are *no* separate fasl files for XLISP and LISP -- 
a buggy fasl file is a buggy fasl file, even if the lisp into which it
is loaded masks the problem.  Re
    Date: 1 December 1980 04:51-EST
    From: Kent M. Pitman <KMP at MIT-MC>
    This is also `fixed' in Lisp if you have done a complex SETF that causes
    SETF FASL to load. Eg, .  .  .   I bring this up not because
    I care about this instance, but it does bother me that we have no mechanism
    for filenaming or autoloading which allows us to separate the FASL files used
    by XLisp from the FASL files used by Lisp. I think this should be thought out
    more carefully and a real solution worked out.
It has always been true (sadly) that there was a divergence between the
FSUBR SETF and the macro;  at one time even, there was a majority opinion
that the value of SETF should be undefined.