SDL: added safeguard for clearOverlay() if overlay is closed
SDL: don't call error() inside setupScreen(), it will crash if debugger is used
SDL: add support for SDL2
SDL2: added support for mdvc
SDL2: revert makefile enable SDL2 to original. added instead disabling SDL audio in source code to be compatible with MSVC
SDL2: changed way how to deal with forbidden symbols
SDL2: added comment to SDL win32
SDL2: use dynamic cast
SDL2: make OpenGL forward compatible
SDL2: changed error messages, SDL return his own.
SDL2: disabled GL forward compatible mode, it seems fail create context on 3.0 GL driver, probably because not setting version of context
SDL2: added/updated few comments
SDL2: changed way to handle with context profile
SDL2: replaced error() calls in setupScreen() to prevent crash