Fixed copyright notice to not mention GNU MP. XXX: Review

all nettle copyrights.

Rev: src/nettle/aes.h:1.2

aes.h

@@ -12,7 +12,7 @@
  * the Free Software Foundation; either version 2.1 of the License, or (at your
  * option) any later version.
  * 
- * The GNU MP Library is distributed in the hope that it will be useful, but
+ * The nettle library is distributed in the hope that it will be useful, but
  * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
  * License for more details.