add license to sprit.cpp

sprit.cpp

@@ -1,3 +1,20 @@
+// sprit-forth: A portable subroutine-threaded Forth.
+// Copyright (C) 2023  Clyne Sullivan <clyne@bitgloo.com>
+//
+// This library is free software; you can redistribute it and/or modify it
+// under the terms of the GNU Library General Public License as published by
+// the Free Software Foundation; either version 2 of the License, or (at your
+// option) any later version.
+//
+// This library 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 Library General Public License for
+// more details.
+//
+// You should have received a copy of the GNU Library General Public License
+// along with this library; if not, write to the Free Software Foundation, Inc.,
+// 51 Franklin St, Fifth Floor, Boston, MA  02110-1301, USA.
+
 #include <algorithm>
 #include <iostream>
 #include <string>