Update COPYING with new address of the FSF.

COPYING

@@ -2,7 +2,8 @@
                        Version 2, June 1991
 
  Copyright (C) 1989, 1991 Free Software Foundation, Inc.
-                          675 Mass Ave, Cambridge, MA 02139, USA
+ 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA
+ 
  Everyone is permitted to copy and distribute verbatim copies
  of this license document, but changing it is not allowed.
 

ChangeLog

@@ -368,6 +368,7 @@ Version 1.5.1 -- CVS
     not enabled in the config.
   - Security: fix several cross site scripting (XSS) attacks. Thanks go to
     Martijn Brinkers for finding a lot of these. [CAN-2005-1769]
+  - Update COPYING with new address of the FSF.
 
 Version 1.5.0 - 2 February 2004
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