PATCH: Display (additional) inline parts

[Toralf Lund <toralf kscanners com>]

The attached patch attempts to modify the message preview code so that more
than one part may be visible at at time; in addition to the one selected,
"inline" parts on the "same level" will be displayed. The idea is mainly to
show the contents of correctly forwarded messages (refer to last week's
discussion on the list) directly.


Comments:

1. The approach taken will work only in the simple case. The problem is
that body list will be looped directly from current part. That's not quite
what we want, we should really start at the "surrounding" "multipart/mixed"
part.
2. It should probably be possible to enable or disable the new behviour in
Preferences.
3. The way parts are related should also be visualised somehow in the icon
list. Perhaps we even want to be able to select the "parent" - and display
all its inline parts when we do - rather than looking for siblings of
simple parts.
4. The message widgets are added to BalsaMessage::content of GtkVBox type
rather than directly to the table. I think older revisions of the code did
just that, but someone must have changed it. Why?
5. And as usual, I don't make any claims about the quality of the actual
code, but I think the functionality it introduces is definitely needed.


-- 
Toralf Lund <toralf@kscanners.com>  +47 66 85 51 22
Kongsberg Scanners AS               +47 66 85 51 00 (switchboard)
http://www.kscanners.no/~toralf     +47 66 85 51 01 (fax)