* menu: replace gtk_menu_popup() with gtk_menu_popup_at_rect()

Replace deprecated gtk_menu_popup() with gtk_menu_popup_at_rect(). This
provides the same menu positioning calculation while eliminating
deprecation warnings.

* ui: replace gtk_widget_get_realized() with gtk_widget_get_mapped()

Replace deprecated gtk_widget_get_realized() with
gtk_widget_get_mapped(). Since mapped widgets are guaranteed to be
realized, and we only care about widget visibility, this change
eliminates deprecation warnings while maintaining the same
functionality.

* frames: replace gdk_window_process_all_updates() with gdk_display_flush()

Replace deprecated gdk_window_process_all_updates() with
gdk_display_flush(). Both functions ensure pending updates are
processed, but gdk_display_flush is more general for all display
requests.

find . \( -name '*.h' -o -name '*.c' \) -exec sed -i 'N;/^\n$/D;P;D;' {} \;

It removes --enable-more-warnings, since it is recommended to use
--enable-compile-warnings=maximum