Only initialize BBDB for message-mode

Being asked all the time whether to add the contact of the current message to BBDB is annoying.

init.el

@@ -1538,7 +1538,7 @@ Note that this workaround is incomplete, as explained in this comment."
             (require 'db-mail)
 
             (with-demoted-errors "Setting up BBDB failed: %s"
-              (bbdb-initialize 'gnus 'message)
+              (bbdb-initialize 'message)
               (bbdb-mua-auto-update-init 'gnus 'message))
 
             ;; Ensure that whenever we compose new mail, it will use the correct posting style.