I was confused about this also, but this post
by Robby Workman and the post above it
by Alien Bob cleared things up for me.
If you're running slackware-current, you should upgrade aaa_elflibs *before* upgrading anything else. You should also upgrade it if you are upgrading between two stable slackware releases (e.g. 13.1 to 13.2). The package should never be removed or reinstalled