Implement workaround for ReaLearn monitoring FX parameter feedback/learning

[helgoboss]

At the moment, REAPER is not capable of notifying extensions of changes of FX in the monitoring FX chain. One effect is that we won't get feedback/learning for FX parameters of FX which is on the monitoring FX chain. This also affects ReaLearn itself being on the monitoring FX chain. Hence, we can't for example get feedback for changing of parameters, which is a pity because then conditional activation works slightly less nicely.

However, I think there's something we can do about it! The ReaLearn instance itself could trigger the global event because it itself is notified of parameter changes.