this fixes the quoted-printable or base64 selector function in
mm-encode.el.  the pgnus-0.96 function is totally broken.
the new improved function is

(defun mm-qp-or-base64 ()
  (save-excursion
    (let ((limit (min (point-max) (+ 2000 (point-min))))
	  (n8bit 0))
      (goto-char (point-min))
      (skip-chars-forward "\x20-\x7f\r\n\t" limit)
      (while (< (point) limit)
	(incf n8bit)
	(forward-char 1)
	(skip-chars-forward "\x20-\x7f\r\n\t" limit))
      (if (< (* 6 n8bit) (- limit (point-min)))
	  'quoted-printable
	'base64))))

which fixes the following problems with the old function.

* long attachments are always quoted-printable

  the old function used narrow to limit to 1000 chars and then
  compared number of 8 bit chars divided by the buffer-size to 0.1667.
  buffer-size is the complete non-narrowed buffer which causes
  quoted-printable to always be chosen for long attachments.

* empty attachment causes divide by zero.

* distinction between multibyte and non-multibyte.

  imho this just added complexity and maintainance headaches without
  buying any useful performance.

* gratuitous usage of floating point.