Overall speedup when using many buffers.

Overall speedup when using many buffers.
(uniquify-fix-item-base, uniquify-fix-item-filename,
uniquify-fix-item-buffer): Changed defmacro to defalias (cosmetic change).
(uniquify-fix-item-unrationalized-buffer): Deleted: was the fourth
place in the item, but waas never used.
(uniquify-fix-item-min-proposed): New defalias: the fourth place
in the item is now used as cache for the proposed name.
(uniquify-rationalize-file-buffer-names): Move computation made on
newbuffile out of the loop, in the newbuffile-nd local var.  Use
dolist (cosmetic change).  Compute the proposed name for the most
common case and cache it in the fourth place in the item.
(uniquify-rationalize-file-buffer-names): Used to return a list
of flags indicating renamed buffers, but that return value was
never used.
(uniquify-item-lessp): Replaces uniquify-filename-lessp, works on
the cached proposed name, does much less consing and is quicker.
(uniquify-filename-lessp): Deleted.
(uniquify-rationalize-a-list): Use dolist (cosmetic change).  Do
not bind locally the uniquify-possibly-resolvable flag.  Use the
cached proposed name if possible.
(uniquify-get-proposed-name): Arguments changed, callers changed.
(uniquify-rationalize-conflicting-sublist): Explicitely reset the
uniquify-possibly-resolvable flag, which is no more bound locally.
(uniquify-rename-buffer): Do not set the unrationalised-buffer
flag, which is replaced by the cached proposed name.