Add notes to SDL_Quit atexit call

Co-authored-by: Eldred Habert <eldredhabert0@gmail.com>

SDL/main.c

@@ -1052,7 +1052,9 @@ int main(int argc, char **argv)
 #endif
 
     SDL_Init(SDL_INIT_EVERYTHING & ~SDL_INIT_AUDIO);
-    atexit(SDL_Quit);
+    // This is, essentially, best-effort.
+    // This function will not be called if the process is terminated in any way, anyhow.
+    (void)atexit(SDL_Quit);
 
     if ((console_supported = CON_start(completer))) {
         CON_set_repeat_empty(true);