[FFmpeg-devel] threadmessage improvements

[Clément Bœsch]

So I've been playing with threadmessage a bit. Since I'm trying to extend the
API for (currently) external usage, I'm also adding an API test.

I've been triggering deadlocks thoughm, typically by setting queue_size=1. I
haven't investigated but I think the issue lies in the fact that there is a
single condition to deal with both growing and shrinking the queue. Or maybe
that's because I broke the API or misuse it...

(Yes this is a WIP, it's missing APIChanges updates and version bump at least)