Improve reliability of menu bar updates on Haiku

Improve reliability of menu bar updates on Haiku

* src/haiku_support.cc (class EmacsWindow): New fields
`menu_update_cv', `menu_update_mutex' and `menu_updated_p'.
(~EmacsWindow): Destroy cv and mutex.
(MenusBeginning): Release lock and wait for condition to be
become true.
(EmacsWindow_signal_menu_update_complete): New function.
* src/haiku_support.h (struct haiku_menu_bar_state_event): New
field `no_lock'.
* src/haikumenu.c (Fhaiku_menu_bar_open): Always update menu
bar.
* src/haikuterm.c (haiku_read_socket): Always update menu bar
and signal the window thread after update completion.