Dynamically allocate long text for SDL_EVENT_TEXT_INPUT events

This prevents input text from being split across Unicode combining or modifier characters, and in practice allocations will rarely happen.

test/testcontroller.c

@@ -1728,6 +1728,7 @@ static void loop(void *arg)
                     AddControllerNameText(event.text.text);
                 }
             }
+            SDL_CleanupEvent(&event);
             break;
         case SDL_EVENT_QUIT:
             done = SDL_TRUE;