Code review comment for lp:~albaguirre/mir/fix-1465883

> So I think Disapprove/Needs fixing. A simple bump of MIRPROTOBUF_ABI will
> solve it more reliably and give us more efficient code. Unless anyone can
> prove there's a protobuf issue preventing us from doing that.

It really isn't that simple: protobuf has a number of issues in this area. Essentially, we can only have one protobuf instantiation in process.

We've "got away" with it while the client ABI has remained at 8 (as only the latest limbirprotobuf gets loaded). Now we're proposing 9 we need to keep the same limbirprotobuf version.

Alexandros has tried to upstream some fixes to protobuf, and Kevin and Chris have recently run into problems.

AFAICS the approach proposed here is the least bad of the feasible options.