[m-rev.] for review: update licensing details on website

[Julien Fischer]

For review by anyone.

--------------------

Update licensing details.

include/download.inc:
     Update the list of library files.

     Mention the static linking exception.

     Bump year in copyright notice.

download/COPYING.LIB:
     Update to the current version.

Julien.

diff --git a/download/COPYING.LIB b/download/COPYING.LIB
index eb685a5..aad3552 100644
--- a/download/COPYING.LIB
+++ b/download/COPYING.LIB
@@ -1,3 +1,29 @@
+In the following, "Mercury Core Libraries" refers to all source
+code in the following directories of this distribution:
+
+    browser, java/runtime, library, mdbcomp, runtime, ssdb, trace
+
+(No other part of this distribution is automatically linked into an
+executable program by the Mercury system.)
+
+The Mercury Core Libraries are distributed under the terms of the
+GNU Library General Public License (LGPL) version 2 (included below).
+
+As a special exception to the GNU Library General Public License, you
+may link, statically or dynamically, a "work that uses the Mercury
+Core Libraries" with the Mercury Core Libraries to produce an
+executable file containing portions of the Mercury Core Libraries,
+and distribute that executable file under terms of your choice,
+without any of the additional requirements listed in clause 6 of the
+GNU Library General Public License. This exception does not however
+invalidate any other reasons why the executable file might be covered
+by the GNU Library General Public License. If you modify the Mercury
+Core Libraries, you may extend this exception to your version, but you
+are not obligated to do so. If you do not wish to do so, delete this
+exception statement from your version.
+
+----------------------------------------------------------------------
+
  		  GNU LIBRARY GENERAL PUBLIC LICENSE
  		       Version 2, June 1991

diff --git a/include/download.inc b/include/download.inc
index 4bff6cb..96147ba 100644
--- a/include/download.inc
+++ b/include/download.inc
@@ -16,7 +16,7 @@ Debian packages are also available, instructions for using them are
  <p>
  The Mercury implementation is free software.<br>
  Copyright © 1993–2012 The University of Melbourne.<br>
-Copyright © 2013–2020 The Mercury team.
+Copyright © 2013–2021 The Mercury team.
  </p>

  <p>
@@ -27,9 +27,10 @@ See the file <a href="download/COPYING">COPYING</a> for copying permission.

  <p>
  The Mercury libraries and runtime (the files in the <samp>library</samp>, <samp>trace</samp>,
-<samp>browser</samp>, <samp>ssdb</samp>, <samp>mdbcomp</samp> and
-<samp>runtime</samp> subdirectories) are distributed under the terms of the
-<a href="http://www.gnu.org/licenses/lgpl-2.0.html">GNU Library General Public License (LGPL)</a>.
+<samp>browser</samp>, <samp>ssdb</samp>, <samp>mdbcomp</samp> ,
+<samp>runtime</samp> and <samp>java/runtime</samp> subdirectories) are distributed under the terms of the
+<a href="http://www.gnu.org/licenses/lgpl-2.0.html">GNU Library General Public License (LGPL)</a>
+with an exception for statically linking against those libraries.
  See the file <a href="download/COPYING.LIB">COPYING.LIB</a> for copying permissions for those files.
  </p>