cdebconf http backend and choice/choice-description independence

[Tollef Fog Heen <tollef@add.no>]

It's amazing what one gets done while on a train, travelling :)

http backend now seems to work, at least for getting the templates.
Setting doesn't work, naturally.  It uses wget for downloading the
templates, and some rearranging in rfc822db exporting the stanza
parsing functions to src/rfc822.c; I'll get template_load to use those
as well, since they are, IMNSHO, a lot better than having two rfc822
parsers (one generic and one specialized) in cdebconf.

As a bonus, I added support for Choices having a
Choices-Description-field, which is used instead of the normal choices
field if it is available.  That means that whatever values main-menu
and friends work with internally does _not_ have to be the same as the
values displayed to the user.

Those aren't checked in yet; I'll send patches here for the
Choices-Description so people have a chance to complain ;)

-- 
Tollef Fog Heen                                                        ,''`.
UNIX is user friendly, it's just picky about who its friends are      : :' :
                                                                      `. `' 
                                                                        `-