bug#16035: 24.3.50; Custom isearch broken on trunk (e.g. change-log-mode)

[Juri Linkov]

> Now I discovered another case that fails to move point
> after exiting Isearch.  Running `multi-isearch-buffers'
> and typing e.g. `C-a' exits Isearch but doesn't move point
> to the beginning of the line.
>
> Exactly the same problem exists in `dired-isearch-filenames'
> that let-binds `dired-isearch-filenames' and calls `isearch-forward'
> without NO-RECURSIVE-EDIT.  And in `comint-history-isearch-backward'
> that let-binds `comint-history-isearch'.

I fixed this case as well.  Multi-buffer and multi-file search
can set the buffer list globally.  And comint.el and dired-aux.el
don't need the global value - they use the let-bound value
only in a setup hook.