Move provide to end of file.

Move provide to end of file.
(uniquify-ref-base, uniquify-ref-filename, uniquify-ref-buffer)
(uniquify-ref-proposed, uniquify-set-proposed): Remove.
(uniquify-item): New struct.  Update users of uniquify-ref-*.
(uniquify-get-proposed-name, uniquify-rationalize-a-list):
Make `depth' optional.
(uniquify-non-file-buffer-names): Remove.
(uniquify-rationalize-file-buffer-names): Don't set it up.
Use uniquify-make-item and don't pass the now-optional depth.
(uniquify-rationalize-conflicting-sublist): Check the new buffer
name directly instead of relying on uniquify-non-file-buffer-names.
(uniquify-rename-buffer): Use with-current-buffer and pass
the `unique' arg to rename-buffer.