SDL_EVENT_QUIT when no window nor tray

SDL_HINT_QUIT_ON_LAST_WINDOW_CLOSE will not fire if there are active tray icons. This impacts only applications that create tray icons, and that at least one icon outlives the last visible top-level window. SDL_EVENT_QUIT will fire when the last active tray is destroyed if there are no active windows.

include/SDL3/SDL_hints.h

@@ -2775,6 +2775,10 @@ extern "C" {
  * - "1": SDL will send a quit event when the last window is requesting to
  *   close. (default)
  *
+ * If there is at least one active system tray icon, SDL_EVENT_QUIT will instead
+ * be sent when both the last window will be closed and the last tray icon will
+ * be destroyed.
+ *
  * This hint can be set anytime.
  *
  * \since This hint is available since SDL 3.1.3.