Change make_invisible_and_set_new_height to be a method

Change make_invisible_and_set_new_height to be a method

This changes make_invisible_and_set_new_height to be a method on
tui_win_info.  I felt that this was cleaner.

gdb/ChangeLog
2019-07-17  Tom Tromey  <tom@tromey.com>

	* tui/tui-win.c (tui_resize_all)
	(tui_source_window_base::update_tab_width)
	(tui_adjust_win_heights): Update.
	(tui_win_info::make_invisible_and_set_new_height): Rename from
	make_invisible_and_set_new_height.
	* tui/tui-data.h (struct tui_win_info)
	<make_invisible_and_set_new_height>: New method.