(local_heap, local_alloc, local_free): New macros.

(local_heap, local_alloc, local_free): New macros.
(malloc_widget_value, free_widget_value)
(w32_free_submenu_strings): Use them.

(push_submenu_start, push_submenu_end, push_left_right_boundary)
(push_menu_pane, push_menu_item, single_keymap_panes)
(single_menu_item, Fx_popup_menu, menubar_selection_callback)
(single_submenu, set_frame_menubar)
(w32_menu_show, w32_dialog_show): Use AREF, ASET, ASIZE.

(Fx_popup_menu):  Don't show pop up menu until preceding one is
actually cleaned up.  Moved UNGCPRO outside #ifdef HAVE_MENUS block.

Changes adapted from xmenu.c
(set_frame_menubar): First parse all submenus,
then make widget_value trees from them.
Don't allocate any widget_value objects
until we are done with the parsing.
(parse_single_submenu): New function.
(digest_single_submenu): New function.
(single_submenu): Function deleted, replaced by those two.