* src/xdisp.c (redisplay_internal): Don't call set_window_update_flags.

* src/xdisp.c (redisplay_internal): Don't call set_window_update_flags.
Set invisible frames's `redisplay' when a full redisplay is requested.
(redisplay_window): Set must_be_updated_p instead.
(redisplay_mode_lines): Don't set must_be_updated_p any more.
(display_mode_lines): Set it here instead.
* src/dispextern.h (set_window_update_flags): Remove.
* src/dispnew.c (set_window_update_flags): Remove `b' argument; make static.

Fixes: debbugs:15999