Introduce has_locator method

Introduce has_locator method

This changes tui_win_has_locator to be a method on tui_win_info, and
changes the locator code to use bool rather than int.

gdb/ChangeLog
2019-06-25  Tom Tromey  <tom@tromey.com>

	* tui/tui-win.c (make_invisible_and_set_new_height)
	(make_visible_with_new_height): Call has_locator method.
	* tui/tui-layout.c (show_source_disasm_command, show_data)
	(show_source_or_disasm_and_command): Update for bool change.
	* tui/tui-data.h (struct tui_source_info) <has_locator>: Now bool.
	(tui_win_info) <has_locator>: New method.
	(struct tui_source_window_base) <has_locator>: New method.
	(tui_win_has_locator): Don't declare.
	* tui/tui-data.c (tui_source_window_base::has_locator): Rename
	from tui_win_has_locator.
	(tui_source_window_base): Use false, not FALSE.