Further progress making Isearch, Ispell, Replace work with Follow Mode.

Further progress making Isearch, Ispell, Replace work with Follow Mode.

* lisp/follow.el: (follow-mode): Remove references to sit*-for-function, which
no longer exists.  Add follow-post-command-hook to  three special purpose
hooks at setup, and remove them at tear down.

* lisp/isearch.el: (isearch-update): invoke isearch-update-post-hook before
isearch-lazy-highlight-new-loop.
(isearch-lazy-highlight-new-loop): Restore this function to what it previously
was, merging the functionality of isearch-lazy-highlight-maybe-new-loop into
it.
(isearch-lazy-highlight-maybe-new-loop): function removed.

* lisp/replace.el: (replace-update-post-hook): New hook variable.
(perform-replace): Add second (nil) argument to looking-back.  Invoke
replace-update-post-hook before calling replace-highlight.

* lisp/textmodes/ispell.el: (ispell-update-post-hook): New hook variable.
(ispell-command-loop): invoke ispell-update-post-hook.  Add GROUP argument to
call of pos-visible-in-window-p.
(ispell-display-buffer): Place *Choices* window at the top of the last window
in a window group.