I was just looking over the changelog for -current. I thought aaa_elflibs wasn't supposed to be upgraded... Anyway the new version number is 13.2 which seems to indicate a second release in the 13 line is maybe coming soon?
Robby has answered your first question. Perhaps I can offer a completely uneducated guess about your second question.
In this update, Pat added LTO
. This requires a new library, libelf, which Pat also added today. The new library will be essential from now on, so a new version of aaa_elflibs was required. And the new aaa_elflibs package has to have a version number, so, logically enough, Pat numbered it 13.2. But I don't think you can take that as an indication of anything else, really.
Interestingly for anyone who follows the SCO affair, this version of libelf is implicated in some of SCO's core accusations in SCO v. IBM. We know this from the recent 'Kevin's Trove' incident.  
So Pat's new update will make using Slackware even more pleasurable, if such a thing is actually possible