MFC r264488:

When merging docsinstall and zfsboot updates to stable/9 it was discovered
that the slightly older dialog(1) requires --separate-output when using the
--checklist widget to force response to produce unquoted values (whereas in
stable/10 --checklist widget without --separate-output will only quote the
checklist labels in the response if the label is multi-word (contains any
whitespace).

Since these enhancements (see revisions 263956 and 264437) were developed
originally on 10, the --separate-output option was omitted. When merged to
stable/9, we (Allan Jude) and I found during testing that the "always-
quoting" of the response was causing things like struct interpolation to
fail (`f_struct device_$dev' would produce `f_struct device_\"da0\"' for
example -- literal quotes inherited from dialog(1) --checklist response).

To see the behavior, execute the following on stable/9 versus stable/10:

        dialog --checklist disks: 0 0 0 da0 "" off da1 "" off

Check both items and hit enter. On stable/10, the response is:

        da0 da1

On stable/9 the response is:

        "da0" "da1"

If you use the --separate-output option, the response is the same for both:

        da0
        da1

So applying --separate-output on every platform until either one of two
things occurs 1) dialog(1,3) gets synchronized between stable/9, higher or
2) we drop support for stable/9.

Reviewed by:    Allan Jude