*: make GNU licensing statement forms more regular

This change retains "or later" state! No licensing _changes_ here,
only form is adjusted (article, space between "GPL" and "v2" and so on).

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/testsuite/tail.tests b/testsuite/tail.tests
index d2427d4..7140da2 100755
--- a/testsuite/tail.tests
+++ b/testsuite/tail.tests
@@ -1,7 +1,7 @@
 #!/bin/sh
 
 # Copyright 2009 by Denys Vlasenko <vda.linux@googlemail.com>
-# Licensed under GPL v2, see file LICENSE for details.
+# Licensed under GPLv2, see file LICENSE in this source tree.
 
 . ./testing.sh