First pass at changing SDL 2.0 to SDL 3.0

cmake/test/main_gui.c

@@ -5,11 +5,11 @@ int main(int argc, char *argv[]) {
     SDL_Window *window = NULL;
     SDL_Surface *screenSurface = NULL;
     if (SDL_Init(SDL_INIT_VIDEO) < 0) {
-        fprintf(stderr, "could not initialize sdl2: %s\n", SDL_GetError());
+        fprintf(stderr, "Could not initialize SDL: %s\n", SDL_GetError());
         return 1;
     }
     window = SDL_CreateWindow(
-            "hello_sdl2",
+            "Hello SDL",
             SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED,
             640, 480,
             SDL_WINDOW_SHOWN