bug#6205: 23.1; align.el error deleting a lot of whitespace

[Kevin Ryde]

If M-x align deletes a lot of whitespace doing its alignment it can get
an "Invalid search bound" error.  Eg. with foo.el below

    emacs -Q foo.el
    M-x end-of-buffer
    M-x align
    => Invalid search bound (wrong side of point)

In `align-region' it seems `last-point' is established from `b' which is
an integer buffer position but that position is invalidated by
whitespace deletes before that point (done by `align-regions').

I get some joy from making the marker before changing the buffer, per
below.  Alternately (untested!) perhaps `b' could be a marker to start
with, ready to be the new value of `last-point'.

2010-05-17  Kevin Ryde  <user42@zip.com.au>

        * align.el (align-region): For `last-point' take marker of b
        position before align-regions because that function inserts or
        deletes text before there.  In particular fixes "Invalid search
        bound" when there's two sections in the region and alignment in
        the first deletes a lot of whitespace.

foo.el
Description: application/emacs-lisp

align.el.last-point.diff
Description: Text Data

In GNU Emacs 23.1.1 (i486-pc-linux-gnu, GTK+ Version 2.16.5)
 of 2009-09-14 on raven, modified by Debian
configured using `configure  '--build=i486-linux-gnu' '--host=i486-linux-gnu' 
'--prefix=/usr' '--sharedstatedir=/var/lib' '--libexecdir=/usr/lib' 
'--localstatedir=/var/lib' '--infodir=/usr/share/info' 
'--mandir=/usr/share/man' '--with-pop=yes' 
'--enable-locallisppath=/etc/emacs23:/etc/emacs:/usr/local/share/emacs/23.1/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/23.1/site-lisp:/usr/share/emacs/site-lisp:/usr/share/emacs/23.1/leim'
 '--with-x=yes' '--with-x-toolkit=gtk' '--with-toolkit-scroll-bars' 
'build_alias=i486-linux-gnu' 'host_alias=i486-linux-gnu' 'CFLAGS=-DDEBIAN -g 
-O2' 'LDFLAGS=-g' 'CPPFLAGS=''

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_AU
  value of $XMODIFIERS: nil
  locale-coding-system: iso-latin-1-unix
  default-enable-multibyte-characters: t