More uses of scoped_restore

More uses of scoped_restore

There were a few more places in gdb that could easily use
scoped_restore, replacing some cleanups.

ChangeLog
2017-08-03  Tom Tromey  <tom@tromey.com>

	* reverse.c (exec_direction_default): Remove.
	(exec_reverse_once): Use scoped_restore.
	* remote.c (restore_remote_timeout): Remove.
	(remote_flash_erase, remote_flash_write, remote_flash_done)
	(readchar, remote_serial_write): Use scoped_restore.
	* cli/cli-script.c (struct source_cleanup_lines_args)
	(source_cleanup_lines): Remove.
	(script_from_file): Use scoped_restore.
	* cli/cli-cmds.c (source_verbose_cleanup): Remove.
	(source_command): Use scoped_restore.