*: 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>

coreutils/ls.c

@@ -3,7 +3,7 @@
  * tiny-ls.c version 0.1.0: A minimalist 'ls'
  * Copyright (C) 1996 Brian Candler <B.Candler@pobox.com>
  *
- * 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.
  */
 
 /* [date unknown. Perhaps before year 2000]