Redisplay "invisible" frames that are actually visible on modern X

Redisplay "invisible" frames that are actually visible on modern X

* etc/NEWS: Document that "invisible" frames are now redisplayed
if the compositing manager is still displaying it as part of a
thumbnail out of Emacs's control.

* src/dispnew.c (Fredraw_display): Use FRAME_REDISPLAY_P.
* src/frame.h (FRAME_REDISPLAY_P): New macro.

* src/xdisp.c (clear_garbaged_frames, echo_area_display)
(prepare_menu_bars, redisplay_internal, display_and_set_cursor)
(gui_clear_cursor): Use FRAME_REDISPLAY_P to determine whether
or not a frame should be redisplayed.
* src/xfns.c (Fx_create_frame): Set visibility state initially.
* src/xterm.c (handle_one_xevent): Likewise.
* src/xterm.h (struct x_output): New field `visibility_state'.