Use scoped_restore for ui_file

Use scoped_restore for ui_file

This replaces all the uses of make_cleanup_restore_ui_file with
scoped_restore.

2016-10-21  Tom Tromey  <tom@tromey.com>

	* utils.c (make_cleanup_restore_ui_file, do_restore_ui_file)
	(struct restore_ui_file_closure): Remove.
	* utils.h (make_cleanup_restore_ui_file): Don't declare.
	* guile/scm-ports.c (ioscm_with_output_to_port_worker): Use
	scoped_restore.
	* top.c (execute_command_to_string): Use scoped_restore.