latest win10 spectre mitigations

[jpf 14]

I eventually let KB4489899 remain installed and on a whim got rid of a whole load of AI aircraft. I can't offer anything definitive except 'maybe' that rogue AI models can be detrimental to performance.
anyway performance is back better than before and ground textures look crisper across the board.

[SKEWR 364]

I followed Jim's advice and I'm back in business with 2 flights completed. We'll see what happens with more flights.