imap-read-passwd fails on Emacs 20.2

[Yoshiki Hayashi <g740685@komaba.ecc.u-tokyo.ac.jp>]

nnimap 0.103 doesn't run on Emacs 20.2. It fails to find
read-passwd because there's no such function in Emacs 20.2

(defun imap-read-passwd (prompt &rest args)
  "Read a password using PROMPT. If ARGS, PROMPT is used as an
argument to `format'."
  (let ((prompt (if args
		    (apply 'format prompt args)
		  prompt)))
    (funcall (if (or (fboundp 'read-passwd)
		     (load "subr" t)
		     (load "passwd" t))
		 'read-passwd
	       'ange-ftp-read-passwd) prompt)))

(fboundp 'read-passwd) ==> nil
(load "subr" t)  ==> t
(load "passwd" t) ==> nil
again, 
(fboundp 'read-passwd) ==> nil

Also, ange-ftp-read is not auto-loaded, 
(funcall 'ange-ftp-read-passwd prompt)
fails.

-- 
Yoshiki Hayashi