newbie can't build

[David Anderson <anderson@merl.com>]

I just downloaded nnimap 0.81, and can't get it to build, as it can't
find base64. I have emacs 20.2 and gnus 5.5. Do I need later versions,
or is the problem something else?

  emacs -batch -q -no-site-file -eval \
    '(if (not (string-match "" "")) \
    (setq load-path (cons "" load-path)))' \
    -l rfc2104.elc -f batch-byte-compile imap.el
  While compiling toplevel forms in file \
    /homes/anderson/nnimap-0.81/imap.el:
    !! File error (("Cannot open load file" "base64"))
  Done
  make: *** [imap.elc] Error 1

--david