change license notices of autobuild script headers

In order to follow GNU suggestion stated here:
http://www.gnu.org/licenses/gpl-howto.html

autobuild/build.sh

@@ -3,15 +3,20 @@
 # SynfigStudio build script
 # Copyright (c) 2008-2018 Konstantin Dmitriev
 #
-# This package 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 file is part of Synfig.
 #
-# This package is distributed in the hope that it will be useful,
+# Synfig 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.
+#
+# Synfig 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.
+# 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 Synfig.  If not, see <https://www.gnu.org/licenses/>.
 
 # = Usage: =
 #    ./build.sh [package] [mode]

autobuild/synfigstudio-cygwin-mingw-build.sh

@@ -3,15 +3,20 @@
 # SynfigStudio Windows package build script
 # Copyright (c) 2013 Konstantin Dmitriev
 #
-# This package 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 file is part of Synfig.
 #
-# This package is distributed in the hope that it will be useful,
+# Synfig 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.
+#
+# Synfig 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.
+# 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 Synfig.  If not, see <https://www.gnu.org/licenses/>.
 #
 #
 # = Usage notes =

autobuild/synfigstudio-osx-build.sh

@@ -4,15 +4,20 @@
 # Copyright (c) 2008-2009 Simone Karin Lehmann (GimpOSX parts)
 # Copyright (c) 2012-2013 Konstantin Dmitriev
 #
-# This package 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 file is part of Synfig.
 #
-# This package is distributed in the hope that it will be useful,
+# Synfig 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.
+#
+# Synfig 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.
+# 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 Synfig.  If not, see <https://www.gnu.org/licenses/>.
 #
 #
 # = Usage notes =