Add GNU classpath exception to repo license (#271)

LICENSE

@@ -337,3 +337,21 @@ proprietary programs.  If your program is a subroutine library, you 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.
+
+
+                  "CLASSPATH" EXCEPTION TO THE GPL
+
+Linking this library statically or dynamically with other modules is making a
+combined work based on this library. Thus, the terms and conditions of the GNU
+General Public License cover the whole combination.
+
+As a special exception, the copyright holders of this library give you
+permission to link this library with independent modules to produce an
+executable, regardless of the license terms of these independent modules, and
+to copy and distribute the resulting executable under terms of your choice,
+provided that you also meet, for each linked independent module, the terms and
+conditions of the license of that module. An independent module is a module
+which is not derived from or based on this library. If you modify this library,
+you may extend this exception to your version of the library, but you are not
+obligated to do so. If you do not wish to do so, delete this exception
+statement from your version.