CMakeLists.txt: Modified to link system wide SDL2 libraries and link to
system wide headers
SplashScreen.cpp: commented out as its post SDL2.0.4 >> SDL_WINDOW_SKIP_TASKBAR
This was a _ton_ of changes, made 15 years ago, so there are probably some
problems to work out still.
Among others: Engine/Base/Stream.* was mostly abandoned and will need to be
re-ported.
Still, this is a pretty good start, and probably holds a world record for
lines of changes or something. :)