RE: /srv/bzr/emacs/trunk r112347:*doc/lispintro/emacs-lisp-intro.texi(defcustom, defun, simplified-beginning-of-buffer, defvar, Building Robots, Review, save-excursion): `defun' and `defcustom' are now macrosratherthanspecial forms. (Bug#13853)

[Drew Adams]

> > (functionp 'foo) => t
> 
> If it returns t in any Emacs in which macros are not funcall'able,
> functionp is buggy (unless the docstring was also changed, but that
> seems unlikely).  A better test is whether `(funcall 'foo nil)'
> errors.

Yes, not to worry.  It raises an error in Emacs 21 and 20:

Debugger entered--Lisp error:
  (invalid-function (macro lambda (a) 42))
  foo(nil)
  funcall(foo nil)