*: 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/networking/ftpd.c b/networking/ftpd.c
index 0daf9f7..64068e4 100644
--- a/networking/ftpd.c
+++ b/networking/ftpd.c
@@ -4,7 +4,7 @@
  *
  * Author: Adam Tkac <vonsch@gmail.com>
  *
- * Licensed under GPLv2, see file LICENSE in this tarball for details.
+ * Licensed under GPLv2, see file LICENSE in this source tree.
  *
  * Only subset of FTP protocol is implemented but vast majority of clients
  * should not have any problem.