Solution provided by an off-list responder:

>Same problem here. 
>
>To fix it cd to /usr/src/lib/libvers then "make".
>
>Then follow the instructions in the advisory.
>
>It worked for me.

And me too. Thanks!

Is there a way to prevent these kinds of problems when installing 
security advisories? It's clear that the person making the advisories 
has already made lots of libraries first. Is it safe and/or a good 
idea to do a "make" in /usr/src/lib?