Pull 'ensure_valid_optarg' into get_nameless_arg, remove from named.
Pull 'ensure_valid_optarg' into get_nameless_arg, remove from named.

Since get_named_arg relies upon get_nameless_arg, there is no need to
have collect_optarg_for check optarg validity (since get_nameless_arg
already does that).

jesserayadkins/lily,jesserayadkins/lily,FascinatedBox/lily,jesserayadkins/lily,FascinatedBox/lily,FascinatedBox/lily,FascinatedBox/lily