Don't define or bind scroll bar functions if

Don't define or bind scroll bar functions if
x-toolkit-scroll-bars is t.
(x-select-text, x-get-selection-value): Clear
x-last-selected-text-clipboard if x-select-enable-clipboard is
nil.
(PRIMARY): Put mac-scrap-name property.
(mac-select-convert-to-file-url): New function.
(public.file-url): New selection target type.  Add to
selection-converter-alist.
(x-get-selection, x-selection-value): Handle it.
(x-cut-buffer-or-selection-value): New alias.