bug#7599: 24.0.50; gnus nnimap doesn't remember choice for auth-source-create

[François Garillot]

During connection to an IMAP server using nnimap, with no
~/.authinfo.gpg file present, function auth-source-create [1] asks for
login and password, then suggests asks the user if it should save those
credentials to ~/.authinfo.gpg

[1] : http://git.gnus.org/cgit/gnus.git/tree/lisp/auth-source.el

If the user answers no, this choice is not remembered. The preference is
not configurable. A user that wants to manually enter login information
at nnimap startup therefore has to refuse credentials storage every
time.

A way to bypass that confirmation would be a nice usability
improvement.

-- 
FG

In GNU Emacs 24.0.50.1 (i486-pc-linux-gnu, GTK+ Version 2.20.1)
 of 2010-11-16 on elegiac, modified by Debian
 (emacs-snapshot package, version 1:20101116-1)
configured using `configure  '--build' 'i486-linux-gnu' '--host' 
'i486-linux-gnu' '--prefix=/usr' '--sharedstatedir=/var/lib' 
'--libexecdir=/usr/lib' '--localstatedir=/var' '--infodir=/usr/share/info' 
'--mandir=/usr/share/man' '--with-pop=yes' 
'--enable-locallisppath=/etc/emacs-snapshot:/etc/emacs:/usr/local/share/emacs/24.0.50/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/24.0.50/site-lisp:/usr/share/emacs/site-lisp'
 '--without-compress-info' '--with-x=yes' '--with-x-toolkit=gtk' 
'--with-imagemagick=yes' 'build_alias=i486-linux-gnu' 
'host_alias=i486-linux-gnu' 'CFLAGS=-DDEBIAN -DSITELOAD_PURESIZE_EXTRA=5000 -g 
-O2' 'LDFLAGS=-g -Wl,--as-needed' 'CPPFLAGS=''

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: en_US.utf8
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS: nil
  locale-coding-system: utf-8-unix
  default enable-multibyte-characters: t

Major mode: Group

Minor modes in effect:
  gnus-topic-mode: t
  gnus-undo-mode: t
  ido-everywhere: t
  delete-selection-mode: t
  pc-selection-mode: t
  show-paren-mode: t
  tooltip-mode: t
  mouse-wheel-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  column-number-mode: t
  line-number-mode: t
  transient-mark-mode: t