*: 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/util-linux/hexdump.c b/util-linux/hexdump.c
index 3db9111..8c4d521 100644
--- a/util-linux/hexdump.c
+++ b/util-linux/hexdump.c
@@ -6,7 +6,7 @@
  * Copyright (c) 1989
  *	The Regents of the University of California.  All rights reserved.
  *
- * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
+ * Licensed under GPLv2 or later, see file LICENSE in this source tree.
  */
 
 #include "libbb.h"