Creating a full-screen SDL renderer on Windows will keep the screensaver
suspended by DirectX, as is default for full-screen DX applications. However,
for applications that render in windowed-mode, the screensaver will
still kick in, even if SDL_DisableScreenSaver() is called or
SDL_HINT_VIDEO_ALLOW_SCREENSAVER is set to 0 (default). Implementing
a SuspendScreenSaver() function for Win32 fixes this behavior.
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