use screen.h instead of sdlscreen.h, etc.

Create grafx2-win32 MSVC++ project
create keycode.h
various fixes

src/loadsave.c

@@ -61,6 +61,7 @@
 #if defined(USE_SDL) || defined(USE_SDL2)
 #include "sdlscreen.h"
 #endif
+#include "screen.h"
 #include "struct.h"
 #include "windows.h"
 #include "engine.h"