Fix copyright header in gan.c
When I wrote the gan.c, I used the wrong copyright/license header
(AGPLv3+ intead of GPLv2+). This was a mistake and is fixed hereby.
diff --git a/src/gsm/gan.c b/src/gsm/gan.c
index e041936..c71c513 100644
--- a/src/gsm/gan.c
+++ b/src/gsm/gan.c
@@ -2,16 +2,16 @@
* All Rights Reserved
*
* This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU Affero General Public License as published by
- * the Free Software Foundation; either version 3 of the License, or
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program 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 Affero General Public License for more details.
+ * GNU General Public License for more details.
*
- * You should have received a copy of the GNU Affero General Public License
+ * You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
*/