dir-locals.el: set case-label offset to 0

While this is the default, private .emacs files might have it set to
something else. No harm in forcing it to 0.

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Reviewed-by: Kristian Høgsberg <krh@bitplanet.net>

.dir-locals.el

@@ -5,6 +5,7 @@
   (c-file-style . "stroustrup")
   (fill-column . 78)
   (eval . (progn
+	    (c-set-offset 'case-label '0)
 	    (c-set-offset 'innamespace '0)
 	    (c-set-offset 'inline-open '0)))
   )