maint: add license headers

[Akim Demaille]

For both 2.5 and master.

It is my understanding that now it is ok to use
a single simple interval for copyright dates, right?
This is my understanding of

commit 4994b1aab88924f5db960472c2189fa1b46c6778
Author: Jim Meyering <address@hidden>
Date:   Fri Jan 27 10:19:26 2012 +0100

   update-copyright: accept new option: UPDATE_COPYRIGHT_USE_INTERVALS=2

   * build-aux/update-copyright: When UPDATE_COPYRIGHT_USE_INTERVALS=2,
   convert a sequence with gaps to the minimal containing range.
   For example, convert 2000, 2004-2007, 2009 to 2000-2009.
   * tests/test-update-copyright.sh: Test for this.
   The FSF confirmed it is ok to do this, assuming there is at
   least one significant change per year in the affected range:
   http://thread.gmane.org/gmane.comp.lib.gnulib.bugs/29554/focus=29860

0002-maint-add-license-headers.patch
Description: Binary data