Don't hide popups when losing focus

This isn't the behavior on Windows, and this should probably be an application defined behavior.

If we decide we want this globally, it should probably be implemented at a higher level in SDL_OnWindowFocusLost(), and properly handle the transition of focus to a child window.

src/video/x11/SDL_x11events.c

@@ -461,20 +461,6 @@ static void X11_ShowChildren(_THIS, SDL_Window *window)
     }
 }
 
-static void X11_HideChildren(_THIS, SDL_Window *window)
-{
-    for (window = window->first_child; window != NULL; window = window->next_sibling) {
-        if (!(window->flags & SDL_WINDOW_HIDDEN)) {
-            window->driverdata->hidden_by_parent_focus = SDL_TRUE;
-            X11_HideWindow(_this, window);
-        }
-
-        if (window->first_child) {
-            X11_HideChildren(_this, window);
-        }
-    }
-}
-
 static void X11_DispatchFocusIn(_THIS, SDL_WindowData *data)
 {
 #ifdef DEBUG_XEVENTS
@@ -518,9 +504,6 @@ static void X11_DispatchFocusOut(_THIS, SDL_WindowData *data)
 #ifdef SDL_USE_IME
     SDL_IME_SetFocus(SDL_FALSE);
 #endif
-    if (data->window->parent == NULL) {
-        X11_HideChildren(_this, data->window);
-    }
 }
 
 static void X11_DispatchMapNotify(SDL_WindowData *data)