Copy the upvotes, downvotes, and total_votes to the smbmsg_t, replicating
what is done in sbbs_t::scanposts() - these are used by sbbs_t::show_msghdr()
so we need to copy them if we're going to be replicating that functionality
(showing up/down votes and score) in message headers shown with bbs.show_msg()
and bbs.show_msg_header().