* frame.h (struct frame): Remove display_preempted member

* frame.h (struct frame): Remove display_preempted member
since all users are dead long ago.
* nsterm.h (struct x_output): Use the only dummy member.
* w32menu.c (pending_menu_activation): Remove since not
really used.
(set_frame_menubar): Adjust user.
* w32term.h (struct x_output): Drop outdated #if 0 code.
(struct w32_output): Use bitfields for explicit_parent,
asked_for_visible and menubar_active members.  Drop
unused pending_menu_activation member.
* xterm.h (struct x_output): Drop outdated #if 0 code.
Use bitfields for explicit_parent, asked_for_visible,
has_been_visible and net_wm_state_hidden_seen members.