x11: Use the SDL_WindowFlags type instead of Uint32

Uint32 can potentially truncate the flag value, as it is 64 bits in SDL3.

src/video/x11/SDL_x11events.c

@@ -1658,7 +1658,7 @@ static void X11_DispatchEvent(SDL_VideoDevice *_this, XEvent *xevent)
          * expected by SDL and its clients. Defer emitting the size/move events until the corresponding
          * PropertyNotify arrives for consistency.
          */
-        const Uint32 changed = X11_GetNetWMState(_this, data->window, xevent->xproperty.window) ^ data->window->flags;
+        const SDL_WindowFlags changed = X11_GetNetWMState(_this, data->window, xevent->xproperty.window) ^ data->window->flags;
         if (changed & (SDL_WINDOW_FULLSCREEN | SDL_WINDOW_MAXIMIZED)) {
             SDL_copyp(&data->pending_xconfigure, &xevent->xconfigure);
             data->emit_size_move_after_property_notify = true;

src/video/x11/SDL_x11window.c

@@ -283,7 +283,7 @@ static void X11_SetKeyboardFocus(SDL_Window *window, bool set_active_focus)
     }
 }
 
-Uint32 X11_GetNetWMState(SDL_VideoDevice *_this, SDL_Window *window, Window xwindow)
+SDL_WindowFlags X11_GetNetWMState(SDL_VideoDevice *_this, SDL_Window *window, Window xwindow)
 {
     SDL_VideoData *videodata = _this->internal;
     Display *display = videodata->display;

src/video/x11/SDL_x11window.h

@@ -128,7 +128,7 @@ struct SDL_WindowData
 };
 
 extern void X11_SetNetWMState(SDL_VideoDevice *_this, Window xwindow, SDL_WindowFlags flags);
-extern Uint32 X11_GetNetWMState(SDL_VideoDevice *_this, SDL_Window *window, Window xwindow);
+extern SDL_WindowFlags X11_GetNetWMState(SDL_VideoDevice *_this, SDL_Window *window, Window xwindow);
 
 extern bool X11_CreateWindow(SDL_VideoDevice *_this, SDL_Window *window, SDL_PropertiesID create_props);
 extern char *X11_GetWindowTitle(SDL_VideoDevice *_this, Window xwindow);