cdebconf X_SETBACKTITLE command

[Colin Watson <cjwatson@debian.org>]

I've checked in a change to cdebconf adding an X_SETBACKTITLE command.
In the newt frontend, this has the effect of drawing text in the top
left-hand corner of the screen, in the same way that Perl debconf writes
"Debian Configuration" in the top left-hand corner. (At the moment it's
not implemented in any of the other frontends.)

The rationale for this is to support using d-i in ways such as rescue
mode that aren't really installation at all. When you're using it in
such a mode, it's unclear what the state of the installer is: I've seen
users not be able to tell whether they were about to perform an
installation or do something entirely different, because they got no
feedback after booting. Adding an extra note would be one workaround for
this, but it feels crude and isn't desirable in some situations.
X_SETBACKTITLE seems less invasive but yet means that the text stays
around for the lifetime of the frontend, which I think is friendlier.

Since this is a debconf protocol extension, I'm mailing the list to
allow time for review and modifications before uploading.

Cheers,

-- 
Colin Watson                                       [cjwatson@debian.org]