Code cleanup, speed and consing improvements for uniquify.el.

Code cleanup, speed and consing improvements for uniquify.el.
(uniquify-ref-base, uniquify-ref-filename)
(uniquify-ref-buffer, uniquify-ref-proposed): New functions.
(uniquify-fix-item-base, uniquify-fix-item-filename)
(uniquify-fix-item-buffer, uniquify-fix-item-proposed): Deleted.
Callers changed.
(uniquify-set-proposed): Changed to work with a vector item.
(uniquify-rationalize-file-buffer-names): Use a list of arrays for
the fix list, and a list of strings for the non-file buffer
names.  Both changes reduce consing.
(uniquify-rationalize-a-list): Local variable renaming.
(uniquify-rationalize-conflicting-sublist): Use member instead of
assoc.
(uniquify-rename-buffer): Use unless instead of if not.