Add OpenSSL linking exception to the copyright file

COPYING

@@ -672,3 +672,16 @@ may consider it more useful to permit linking proprietary applications with
 the library.  If this is what you want to do, use the GNU Lesser General
 Public License instead of this License.  But first, please read
 <http://www.gnu.org/philosophy/why-not-lgpl.html>.
+
+  In addition, as a special exception, the copyright holders give
+permission to link the code of portions of this program with the
+OpenSSL library under certain conditions as described in each
+individual source file, and distribute linked combinations including
+the two.
+  You must obey the GNU General Public License in all respects for all
+of the code used other than OpenSSL.  If you modify file(s) with this
+exception, you may extend this exception to your version of the
+file(s), but you are not obligated to do so.  If you do not wish to do
+so, delete this exception statement from your version.  If you delete
+this exception statement from all source files in the program, then
+also delete it here.