(popup_get_selection): Queue up events that aren't

(popup_get_selection): Queue up events that aren't
for the menu, and process them afterward.  New arg dpyinfo.
(set_frame_menubar): Use inhibit_garbage_collection.
[USE_X_TOOLKIT] (xmenu_show): Delete the queue code here.
Pass dpyinfo to popup_get_selection.
Don't call lw_destroy_all_widgets.
[USE_X_TOOLKIT] (xdialog_show): Simplify using popup_get_selection.