Fix keyboard.c infloops on circular lists

Fix keyboard.c infloops on circular lists

Fix infinite loops in keyboard.c when a circular list is
found in a hook, or in help-event-list, or in the argument
of event-convert-list, or in a keymap where a Lucid event
type list is expected, or in a menu or tab spec.
* src/keyboard.c (safe_run_hooks_error, menu_bar_items)
(parse_menu_item, parse_tab_bar_item, parse_tool_bar_item):
Use FOR_EACH_TAIL to avoid infloop on circular lists.
(help_char_p, Fevent_convert_list, lucid_event_type_list_p):
Use FOR_EACH_TAIL_SAFE to avoid infloop on circular lists,
when the action is idempotent so a circular list can be
treated as a noncircular one.