groundwork for window port interface change to add_menu

groundwork only - window port interface change

This changes the last parameter for add_menu() from a boolean
to an unsigned int, to allow additional itemflags in future
beyond just the "preselected" that the original boolean offered.

There shouldn't be any functionality changes with this groundwork-only
change, and if there are it is unintentional and should be reported.

src/end.c

@@ -1815,7 +1815,8 @@ set_vanq_order()
             continue;
         any.a_int = i + 1;
         add_menu(tmpwin, NO_GLYPH, &any, 0, 0, ATR_NONE, vanqorders[i],
-                 (i == g.vanq_sortmode) ? MENU_SELECTED : MENU_UNSELECTED);
+                 (i == g.vanq_sortmode)
+                    ? MENU_ITEMFLAGS_SELECTED : MENU_ITEMFLAGS_NONE);
     }
     end_menu(tmpwin, "Sort order for vanquished monster counts");