Remove tui_delete_invisible_windows and tui_make_all_invisible

Remove tui_delete_invisible_windows and tui_make_all_invisible

tui_delete_invisible_windows is only needed after applying a layout,
and tui_make_all_invisible is only needed before applying a layout.

This patch removes these functions, in favor of doing this management
directly in tui_apply_current_layout.  This is needed so that the
lifetimes of non-built-in windows will be properly managed.

gdb/ChangeLog
2020-02-22  Tom Tromey  <tom@tromey.com>

	* tui/tui-wingeneral.h (tui_make_all_invisible): Don't declare.
	* tui/tui-wingeneral.c (tui_make_all_invisible): Remove.
	* tui/tui-win.c (tui_resize_all): Don't call
	tui_delete_invisible_windows.
	* tui/tui-layout.c (tui_apply_current_layout): Delete windows when
	done.
	(tui_set_layout): Update.
	(tui_add_win_to_layout): Don't call tui_delete_invisible_windows.
	* tui/tui-data.h (tui_delete_invisible_windows): Don't declare.
	* tui/tui-data.c (tui_delete_invisible_windows): Remove.

Change-Id: Ia3603b021dcb7ec31700a4a32640cd09b00b8f3b