maint: add license headers.

* examples/calc++/test, examples/variant.yy, AUTHORS, THANKS,
	* tests/atlocal.in, tests/bison.in: Add license headers.
	Reported by Tys Lefering.
(cherry picked from commit 3272a7256f)

Conflicts:

	examples/variant.yy
	tests/bison.in

THANKS

@@ -121,3 +121,22 @@ thank them!  Please, help us keeping this list up to date.
 Local Variables:
 mode: text
 End:
+
+-----
+
+Copyright (C) 2000-2012 Free Software Foundation, Inc.
+
+This file is part of Bison, the GNU Parser Generator.
+
+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 3 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, see <http://www.gnu.org/licenses/>.