*: 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>

scripts/echo.c

@@ -6,7 +6,7 @@
  * Copyright (c) 1991, 1993
  *	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.
  *
  * Original copyright notice is retained at the end of this file.
  */

scripts/mkconfigs

@@ -38,7 +38,7 @@ echo "\
 /*
  * busybox configuration settings.
  *
- * 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.
  *
  * This file is generated automatically by scripts/mkconfigs.
  * Do not edit.

scripts/showasm

@@ -1,7 +1,7 @@
 #!/bin/sh
 
 # Copyright 2006 Rob Landley <rob@landley.net>
-# 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.
 
 # Dumb little utility function to print out the assembly dump of a single
 # function, or list the functions so dumpable in an executable.  You'd think