*: 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>

printutils/Kbuild.src

@@ -1,6 +1,6 @@
 # Makefile for busybox
 #
-# Licensed under the GPL v2, see the file LICENSE in this tarball.
+# Licensed under GPLv2, see file LICENSE in this source tree.
 
 lib-y :=