bsddialog: in textbox mode differentiate between Exit and Extra buttons

[glebius]

Summary

If run --extra-button --textbox dialog will have two buttons, but
either of them would return 0 exit status. We definitely want the
Extra to report its value.

[jlduran]

After a simple:

grep -r -A3 "case 10" contrib/bsddialog/

I could not find any other occurrence that needs fixing.

[asiciliano]

In D48668#1110114, @jlduran wrote:

After a simple:

grep -r -A3 "case 10" contrib/bsddialog/

I could not find any other occurrence that needs fixing.

@jlduran Maybe the checks has to be performed inside the "clients" of bsddialog: bsdinstall, (mainly) bsdconfig, tzsetup, spkrtest, and kdbmap to avoid side effects.
Anyway the @glebius 's change makes sense. Honestly I forgot why textbox always returns OK, maybe for compatibility with cdialog. Anyway the next version (and import in contrib/) of bsddialog will have this change.

contrib/bsddialog/lib/textbox.c

203

Ok, this makes sense, honestly I forgot why textbox always returns OK, maybe compatibility with cdialog. Anyway I'll add 2 more changes/feature requests to bsddialog then I'll import a new version with this change.