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>

Documentation/technical/api-builtin.txt

@@ -39,7 +39,7 @@ where options is the bitwise-or of:
 	on bare repositories.
 	This only makes sense when `RUN_SETUP` is also set.
 
-. Add `builtin-foo.o` to `BUILTIN_OBJS` in `Makefile`.
+. Add `builtin/foo.o` to `BUILTIN_OBJS` in `Makefile`.
 
 Additionally, if `foo` is a new command, there are 3 more things to do:
 

Documentation/technical/api-parse-options.txt

@@ -269,10 +269,10 @@ Examples
 --------
 
 See `test-parse-options.c` and
-`builtin-add.c`,
-`builtin-clone.c`,
-`builtin-commit.c`,
-`builtin-fetch.c`,
-`builtin-fsck.c`,
-`builtin-rm.c`
+`builtin/add.c`,
+`builtin/clone.c`,
+`builtin/commit.c`,
+`builtin/fetch.c`,
+`builtin/fsck.c`,
+`builtin/rm.c`
 for real-world examples.