Disable "The key you just pressed is not recognized by SDL." message by default

src/video/riscos/SDL_riscosevents.c

@@ -40,9 +40,11 @@ SDL_RISCOS_translate_keycode(int keycode)
     if (keycode < SDL_arraysize(riscos_scancode_table)) {
         scancode = riscos_scancode_table[keycode];
 
+#ifdef DEBUG_SCANCODES
         if (scancode == SDL_SCANCODE_UNKNOWN) {
             SDL_Log("The key you just pressed is not recognized by SDL: %d", keycode);
         }
+#endif
     }
 
     return scancode;