[!TARGET_API_MAC_CARBON]: Move includes to mactoolbox.c.

[!TARGET_API_MAC_CARBON]: Move includes to mactoolbox.c.
(enum mac_menu_kind): Move enum to mactoolbox.c.
(min_menu_id): Move variable to mactoolbox.c.
(quit_dialog_event_loop) [TARGET_API_MAC_CARBON]: Likewise.
(DIALOG_WINDOW_RESOURCE): Move define to mactoolbox.c.
(DIALOG_BUTTON_COMMAND_ID_OFFSET, DIALOG_BUTTON_COMMAND_ID_P)
(DIALOG_BUTTON_COMMAND_ID_VALUE, DIALOG_BUTTON_MAKE_COMMAND_ID)
[TARGET_API_MAC_CARBON]: Likewise.
(XtPointer): Move typedef to macgui.h.
(enum button_type): Move enum to macgui.h.
(widget_value): Move typedef to macgui.h.
(DIALOG_LEFT_MARGIN, DIALOG_TOP_MARGIN, DIALOG_RIGHT_MARGIN)
(DIALOG_BOTTOM_MARGIN, DIALOG_MIN_INNER_WIDTH, DIALOG_MAX_INNER_WIDTH)
(DIALOG_BUTTON_BUTTON_HORIZONTAL_SPACE)
(DIALOG_BUTTON_BUTTON_VERTICAL_SPACE, DIALOG_BUTTON_MIN_WIDTH)
(DIALOG_TEXT_MIN_HEIGHT, DIALOG_TEXT_BUTTONS_VERTICAL_SPACE)
(DIALOG_ICON_WIDTH, DIALOG_ICON_HEIGHT, DIALOG_ICON_LEFT_MARGIN)
(DIALOG_ICON_TOP_MARGIN): Move defines to macgui.h.
(popup_activated_flag): Make variable non-static.
(x_activate_menubar, install_menu_quit_handler, pop_down_menu)
(add_menu_item, fill_menu, dispose_menus):
Move functions to mactoolbox.c.
(restore_show_help_function, menu_target_item_handler)
(install_menu_target_item_handler, mac_handle_dialog_event)
(install_dialog_event_handler, pop_down_dialog, create_and_show_dialog)
[TARGET_API_MAC_CARBON]: Likewise.
(menu_quit_handler) [MAC_OS_X_VERSION_MAX_ALLOWED >= 1030]: Likewise.
(mac_dialog) [!TARGET_API_MAC_CARBON]: Likewise.
(find_and_call_menu_selection, name_is_separator): Make function
non-static.
(Vshow_help_function, timer_check) [TARGET_API_MAC_CARBON]: Move extern
to mactoolbox.c.
(set_frame_menubar): Don't call install_menu_quit_handler.
(menu_item_selection): New variable.
(mac_menu_show): Use create_and_show_popup_menu.
(create_and_show_dialog) [TARGET_API_MAC_CARBON]: Don't return
selection but set variable menu_item_selection.  All uses changed.
(mac_fill_menubar): Rename from fill_menubar.  All uses changed.
Call install_menu_quit_handler.  Move to mactoolbox.c.