SDL2: Difficulty debugging on Windows

[historic_bruno]

With SDL2, the game window interferes with debugging in a way that WSDL did not. In fullscreen mode, it's almost impossible to use the debugger because the window keeps focus and remains drawn on top of everything else when a breakpoint is hit. Even in windowed mode, it's problematic. There may not be a good solution to this, but at least it's documented.