Use scoped_restore for current_ui

Use scoped_restore for current_ui

This changes most uses of make_cleanup_restore_current_ui to use
scoped_restore.  The use in switch_thru_all_uis_init still remains;
that is dealt with in a later patch by replacing this iterator with a
real class.

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

	* top.c (new_ui_command, wait_sync_command_done)
	(gdb_readline_wrapper): Use scoped_restore.
	* infrun.c (fetch_inferior_event): Use scoped_restore.
	* infcall.c (call_thread_fsm_should_stop): Use scoped_restore.