* mm-util.el (mm-coding-system-p): Don't return binary for the nil argument in

* mm-util.el (mm-coding-system-p): Don't return binary for the nil argument in
 XEmacs.

* nnrss.el (nnrss-compatible-encoding-alist): New variable.
(nnrss-request-group): Decode group name first.
(nnrss-request-article): Make a text/plain article if mml-to-mime failed.
(nnrss-get-encoding): Return a compatible encoding according to
 nnrss-compatible-encoding-alist.
(nnrss-find-el): Use consp instead of listp.