no-export problem resolved

The problem I had with one of my upstreams' handling of no-export has
been resolved. They were, you'll be happy to hear, full of desire to
do the right thing (and had apparently been doing it until the syntax
for doing so changed out from under them, so clearly you can't turn
your back on those router vendors) and the ticket was closed.

So, yes, my assertion that no-export support was not built-in was
wrong. Mea culpa.