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/replace.c b/builtin/replace.c
index 398ccd5..59d3115 100644
--- a/builtin/replace.c
+++ b/builtin/replace.c
@@ -3,7 +3,7 @@
  *
  * Copyright (c) 2008 Christian Couder <chriscool@tuxfamily.org>
  *
- * Based on builtin-tag.c by Kristian Høgsberg <krh@redhat.com>
+ * Based on builtin/tag.c by Kristian Høgsberg <krh@redhat.com>
  * and Carlos Rica <jasampler@gmail.com> that was itself based on
  * git-tag.sh and mktag.c by Linus Torvalds.
  */