*: 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>

libbb/process_escape_sequence.c

@@ -5,7 +5,7 @@
  * Copyright (C) Manuel Novoa III <mjn3@codepoet.org>
  * and Vladimir Oleynik <dzo@simtreas.ru>
  *
- * 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"