Freeciv

Still a couple of questions that might be worth thinking about:

This breaks if requirements are ever evaluated in a multithreaded context. I feel like this could be a problem with threaded AI? Haven't tested that.

There's an argument to be made that this should be an error rather than a warning. The reason I went with warning is to provide leeway for reasonable behavior that only becomes self-referential when evaluating RPT_POSSIBLE with partial information (example).

Yes, Tex AI can evaluate tiles for autoworkers actions while the main thread does whatever requirement evaluations. Might also do movement (action enabler requirements) related evaluations in the thread.

Adding thread-local storage functionality to fcthreads should not be too hard, if we avoid over-engineering it (something just for our specific use-case)