*: 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/libbb/bb_pwd.c b/libbb/bb_pwd.c
index d728577..32406cb 100644
--- a/libbb/bb_pwd.c
+++ b/libbb/bb_pwd.c
@@ -5,7 +5,7 @@
  * Copyright (C) 1999-2004 by Erik Andersen <andersen@codepoet.org>
  * Copyright (C) 2008 by Tito Ragusa <farmatito@tiscali.it>
  *
- * Licensed under the GPL v2 or later, see the file LICENSE in this tarball.
+ * Licensed under GPLv2 or later, see file LICENSE in this source tree.
  */
 
 #include "libbb.h"