*: 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/editors/cmp.c b/editors/cmp.c
index dbfa4be..f495da7 100644
--- a/editors/cmp.c
+++ b/editors/cmp.c
@@ -4,7 +4,7 @@
  *
  * Copyright (C) 2000,2001 by Matt Kraai <kraai@alumni.carnegiemellon.edu>
  *
- * 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.
  */
 
 /* BB_AUDIT SUSv3 (virtually) compliant -- uses nicer GNU format for -l. */