Add one-line GPL boilerplate to numerous (but not all yet) source files.
diff --git a/archival/libunarchive/data_align.c b/archival/libunarchive/data_align.c
index 1efe9d8..81594d8 100644
--- a/archival/libunarchive/data_align.c
+++ b/archival/libunarchive/data_align.c
@@ -1,18 +1,6 @@
 /* vi: set sw=4 ts=4: */
 /*
- *  This program is free software; you can redistribute it and/or modify
- *  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 General Public License for more details.
- *
- *  You should have received a copy of the GNU General Public License
- *  along with this program; if not, write to the Free Software
- *  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
  */
 
 #include <sys/types.h>