*: 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>

editors/vi.c

@@ -3,7 +3,7 @@
  * tiny vi.c: A small 'vi' clone
  * Copyright (C) 2000, 2001 Sterling Huxley <sterling@europa.com>
  *
- * 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.
  */
 
 /*