bug#5107: 23.1.50; Can't backspace indentions inserted by refill-mode

[Matthew Dempsky <matthew@dempsky.org>]

If you have a buffer using refill-mode with indented text like

    Lorem [...text spanning to the fill column...]
    ipsum...

and the point is right before the `i', then pressing backspace has no
effect.  I.e., to edit "foo\n []bar" (where [] is the point) into
"\n foo[]bar", you can't just press DEL.


In GNU Emacs 23.1.50.1 (i386-apple-darwin9.8.0, NS apple-appkit-949.54)
 of 2009-12-02 on admins-macbook-pro-2.local
Windowing system distributor `Apple', version 10.3.949
configured using `configure  '--with-ns' '--without-x''

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  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: Lisp Interaction

Minor modes in effect:
  refill-mode: t
  tooltip-mode: t
  mouse-wheel-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  global-auto-composition-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent input:
C-u SPC C-x ( L o r e m SPC i p s u m . . . SPC C-x
) M-x r e f i l l - m o d e <return> M-3 M-0 C-x e
C-a C-u C-f <backspace> <backspace> <backspace> <backspace>
<backspace> <backspace> <backspace> <backspace> <backspace>
<backspace> <backspace> <backspace> <backspace> <backspace>
C-h C-g M-` h s

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
Defining kbd macro...
Keyboard macro defined
Refill mode enabled
(Type e to repeat macro)

Load-path shadows:
None found.

Features:
(shadow mail-extr message ecomplete rfc822 mml mml-sec password-cache
mm-decode mm-bodies mm-encode mailcap mail-parse rfc2231 rfc2047 rfc2045
qp ietf-drums mailabbrev nnheader gnus-util netrc time-date mm-util
mail-prsvr gmm-utils wid-edit mailheader canlock sha1 hex-util hashcash
mail-utils emacsbug sendmail regexp-opt help-mode view tmm electric
edmacro refill easy-mmode kmacro tooltip ediff-hook vc-hooks
lisp-float-type mwheel ns-win easymenu tool-bar dnd fontset image fringe
lisp-mode register page menu-bar rfn-eshadow timer select scroll-bar
mldrag mouse jit-lock font-lock syntax facemenu font-core frame cham
georgian utf-8-lang misc-lang vietnamese tibetan thai tai-viet lao
korean japanese hebrew greek romanian slovak czech european ethiopic
indian cyrillic chinese case-table epa-hook jka-cmpr-hook help simple
abbrev loaddefs button minibuffer faces cus-face text-properties overlay
md5 base64 format env code-pages mule custom widget
hashtable-print-readable backquote make-network-process ns multi-tty
emacs)