Fix problems when BBDB is not present and gnorb-bbdb is not loaded.

I'm experimenting with gnorb but have BBDB 2 installed, and therefore don't want to try gnorb's BBDB integration.  I don't load gnorb-bbdb, but still have to make the following changes to run gnorb without errors.

I hope that you find the patch useful.
I don't quite see this is a good idea -- if you don't have BBDB loaded, you shouldn't be calling this function in the first place. In fact, without BBDB loaded, it will signal all sorts of errors, which is why I had the (require 'gnorb-bbdb). I'd almost rather keep that, but then sanitize the function body itself so that it works with both BBDB versions 2 and 3. What do you think?