fix "builtin-*" references to be "builtin/*"

Documentation and some comments still refer to files in builtin/
as 'builtin-*.[cho]'.  Update these to show the correct location.

Signed-off-by: Phil Hord <hordp@cisco.com>
Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Assisted-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/builtin/notes.c b/builtin/notes.c
index 453457a..ac43cbae 100644
--- a/builtin/notes.c
+++ b/builtin/notes.c
@@ -4,7 +4,7 @@
  * Copyright (c) 2010 Johan Herland <johan@herland.net>
  *
  * Based on git-notes.sh by Johannes Schindelin,
- * and builtin-tag.c by Kristian Høgsberg and Carlos Rica.
+ * and builtin/tag.c by Kristian Høgsberg and Carlos Rica.
  */
 
 #include "cache.h"