bug#7179: 23.2; copyright-update on spanning copyright-limit

[Kevin Ryde <user42@zip.com.au>]

If you're unlucky enough to have a copyright notice spanning the
`copyright-limit' position in the buffer then M-x copyright-update makes
a bit of a mess inserting the current year at the wrong place.  For
example,

    (progn
      (require 'copyright)
      (switch-to-buffer "foo")
      (erase-buffer)
      (insert (make-string (- copyright-limit 14) ?x) "\n"
              "\nCopyright 2006, 2007, 2008 Foo Bar\n\n")
      (copyright-update))

gives

    Copyright 20, 1006, 2007, 2008 Foo Bar

where I expected

    Copyright 2006, 2007, 2008, 2010 Foo Bar

I suppose the limit in the re-search-forward means only "Copyright 20"
is matched and the current year ", 10" inserted there.  Perhaps a fresh
`looking-at' or something would ensure the limit doesn't truncate the
optional-ness in the years part of the pattern.

I struck this in a short html file where the copyright line was actually
near the end, yet close enough to the start to be seen by
copyright-update with the copyright-at-end-flag false.  I suppose a
copyright-names-regexp might force a spanning line not to match, but I
had that empty.




In GNU Emacs 23.2.1 (i486-pc-linux-gnu, GTK+ Version 2.20.0)
 of 2010-05-16 on raven, modified by Debian
configured using `configure  '--build' 'i486-linux-gnu' '--build' '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/23.2/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/23.2/site-lisp:/usr/share/emacs/site-lisp:/usr/share/emacs/23.2/leim' '--with-x=yes' '--with-x-toolkit=gtk' '--with-toolkit-scroll-bars' 'build_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