Update headers to explicitly reference GPL version 3

Signed-off-by: Jan Blunck <jblunck@infradead.org>

Build/LiveBuild.pm

@@ -1,21 +1,24 @@
+################################################################
 #
 # Author: Jan Blunck <jblunck@infradead.org>
 #
 # This file is part of build.
 #
-# build 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 free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 2 or 3 as
+# published by the Free Software Foundation.
 #
-# build is distributed in the hope that it will be useful,
+# 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 build.  If not, see <http://www.gnu.org/licenses/>.
+# along with this program (see the file COPYING); if not, write to the
+# Free Software Foundation, Inc.,
+# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
 #
+#################################################################
 
 package Build::LiveBuild;
 

build-recipe-livebuild

@@ -1,23 +1,26 @@
+#################################################################
 #
 # Debian live-build specific functions.
 #
 # Author: Jan Blunck <jblunck@infradead.org>
 #
 # This file is part of build.
 #
-# build 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 free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 2 or 3 as
+# published by the Free Software Foundation.
 #
-# build is distributed in the hope that it will be useful,
+# 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 build.  If not, see <http://www.gnu.org/licenses/>.
+# along with this program (see the file COPYING); if not, write to the
+# Free Software Foundation, Inc.,
+# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
 #
+#################################################################
 
 recipe_setup_livebuild() {