BTW, according to (elisp) Function Cells:

     Note that void is not the same as ‘nil’ or the symbol ‘void’.  The
  symbols ‘nil’ and ‘void’ are Lisp objects, and can be stored into a
  function cell just as any other object can be (and they can be valid
  functions if you define them in turn with ‘defun’).  A void function
  cell contains no object whatsoever.

So I suppose that means that the old `fmakunbound' docstring was
incorrect in saying: "Make SYMBOL's function definition be nil."?

Best regards,
Stefan Kangas