Bastien writes:
> There is already this in org-macs.el:
>
> (when (and (not (fboundp 'with-silent-modifications))
> 	   (or (< emacs-major-version 23)
> 	       (and (= emacs-major-version 23)
> 		    (< emacs-minor-version 2))))
>   (defmacro with-silent-modifications (&rest body)
>     `(org-unmodified ,@body))
>   (def-edebug-spec with-silent-modifications (body)))

We shouldn't define things that don't have an org prefix.  I don't
really see why we needed to replace org-unmodified in the first place,
especially since with-silent-modifications does _more_ than
org-unmodified, not less as your comment in org-macs would imply.
Here's a patch to restore org-unmodified in the sources, make it an
alias to with-silent-modifications when possible and augment the
replacement definition with a few things that with-silent-modifications
does on top of what org-unmodified did.  We might even copy the whole
macro definition from subr.el, but I think we're close enough with this.