bug#14994: 24.3; gnus-completing-read in smime.el fails to complete

[Katsumi Yamaoka]

Stefan Monnier wrote:
>> +                     ;; Old XEmacs (at least 21.4) expect an alist,
>> +                 ;; in which the car of each element is a string,
>> +                 ;; for collection.
>> +                     (mapcar (lambda (elem)
>> +                           (list (format "%s" (or (car-safe elem) elem))))
>> +                         collection)
>>                       nil require-match initial-input history def)))

> I recommend you wrap this in an (if (featurep 'xemacs) ...) so as to
> avoid using this code when it's not needed.  After all, it looks both
> inefficient and hackish.

Indeed.  I've simply isolated it as an XEmacs stuff.