Use scoped_restore in more places

Use scoped_restore in more places

This changes a few more places to use scoped_restore, allowing some
cleanup removals.

gdb/ChangeLog
2017-04-12  Tom Tromey  <tom@tromey.com>

	* mi/mi-main.c (exec_direction_forward): Remove.
	(exec_reverse_continue, mi_execute_command): Use scoped_restore.
	* guile/scm-ports.c (ioscm_with_output_to_port_worker): Use
	scoped_restore.
	* guile/guile.c (guile_repl_command, guile_command)
	(gdbscm_execute_gdb_command): Use scoped_restore.
	* go-exp.y (go_parse): Use scoped_restore.
	* d-exp.y (d_parse): Use scoped_restore.
	* cli/cli-decode.c (cmd_func): Use scoped_restore.
	* c-exp.y (c_parse): Use scoped_restore.