tsearch: Relicense under LGPLv2+

[Bruno Haible]

I need the module 'tsearch' under LGPLv2+, for use in GNU libintl.
Fortunately it is easy to do, because
  - It was under LGPLv2+ when I took the source code from glibc in 2006 (see
    <https://lists.gnu.org/archive/html/bug-gnulib/2006-10/msg00308.html>).
  - The only significant changes to lib/tsearch.c since then are from me.


2021-06-16  Bruno Haible  <bruno@clisp.org>

        tsearch: Relicense under LGPLv2+.
        * modules/tsearch (License): Change to LGPLv2+.
        * lib/tsearch.c: Update license notice.

diff --git a/lib/tsearch.c b/lib/tsearch.c
index 08f7061..0d4d838 100644
--- a/lib/tsearch.c
+++ b/lib/tsearch.c
@@ -7,7 +7,7 @@
 
    This file is free software: you can redistribute it and/or modify
    it under the terms of the GNU Lesser General Public License as
-   published by the Free Software Foundation; either version 3 of the
+   published by the Free Software Foundation; either version 2.1 of the
    License, or (at your option) any later version.
 
    This file is distributed in the hope that it will be useful,
diff --git a/modules/tsearch b/modules/tsearch
index 4a2b5ed..6ffdf2f 100644
--- a/modules/tsearch
+++ b/modules/tsearch
@@ -22,7 +22,7 @@ Include:
 <search.h>
 
 License:
-LGPL
+LGPLv2+
 
 Maintainer:
 all, glibc