Add SDL high DPI config

[slightc]

when I run the simulator on macbook, after reduce the SDL_ZOOM, the screen will become will become extremely blurry, that need add SDL_WINDOW_ALLOW_HIGHDPI flag to resolve it when create SDL Window

that result of add SDL_WINDOW_ALLOW_HIGHDPI flag

so, I think could add SDL_HIGHDPI micro define to config the flag?

Hope for your response, thanks!

[stale]

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