libdpkg: Fix inadvertent license change back from GPL2 to GPL2+

In commit b95907e6e0f3f25136fb2ebcc8d3489efb208dea, several functions
were refactored out from src/filesdb.c (with a GPL2+ license), into
lib/utils.c (with a GPL2 license), inadvertently making them change
license.

Ian clarified that this was a mistake in:

  <https://lists.debian.org/debian-dpkg/2015/08/msg00029.html>

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>
Signed-off-by: Guillem Jover <guillem@debian.org>

debian/changelog

@@ -18,6 +18,7 @@ dpkg (1.18.3) UNRELEASED; urgency=low
   * Split overlong perl regexes into multiline extended regexes.
   * Switch dselect multicd method license from GPL2 to GPL2+, with consent
     from all its authors.
+  * Fix inadvertent license change for lib/dpkg/utils.c from GPL2 to GPL2+.
   * Perl modules:
     - Only warn on invalid week days instead of aborting in
       Dpkg::Changelog::Entry::Debian. Regression introduced in dpkg 1.18.2.

debian/copyright

@@ -6,7 +6,7 @@ Copyright:
  Copyright © 1994 Ian Murdock <imurdock@debian.org>
  Copyright © 1994 Matt Welsh <mdw@sunsite.unc.edu>
  Copyright © 1994 Carl Streeter <streeter@cae.wisc.edu>
- Copyright © 1994-1999 Ian Jackson <ian@chiark.greenend.org.uk>
+ Copyright © 1994-1999, 2008 Ian Jackson <ian@chiark.greenend.org.uk>
  Copyright © 1995 Bruce Perens <bruce@pixar.com>
  Copyright © 1995-1996 Erick Branderhorst <branderhorst@heel.fgg.eur.nl>
  Copyright © 1996 Michael Shields <shields@crosslink.net>
@@ -52,12 +52,6 @@ Copyright:
  Copyright © 1987-2006 Free Software Foundation, Inc.
 License: GPL-2+
 
-Files:
- lib/dpkg/utils.c
-Copyright:
- Copyright © 2008 Ian Jackson <ian@davenant.greenend.org.uk>
-License: GPL-2
-
 Files:
  dselect/methods/Dselect/Ftp.pm
  dselect/methods/ftp/*

lib/dpkg/utils.c

@@ -2,9 +2,12 @@
  * libdpkg - Debian packaging suite library routines
  * utils.c - helper functions for dpkg
  *
+ * Copyright © 1995, 2008 Ian Jackson <ian@chiark.greenend.org.uk>
+ *
  * This is free software; you can redistribute it and/or modify
- * it under the terms of version 2 of the GNU General Public
- * License version 2 as published by the Free Software Foundation.
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
  *
  * This is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of