cut: simplify and remove an IF_LINT

cut: simplify and remove an IF_LINT

* src/cut.c (enum operating_mode, operating_mode)
(output_delimiter_specified, cut_stream):
Remove; no longer needed.
(output_delimiter_default): New static var.  Code can now
use ‘output_delimiter_string != output_delimiter_default’
instead of ‘output_delimiter_specified’.
(cut_file): New arg CUT_STREAM.  Caller changed.
(main): Simplify.  Coalesce duplicate code.  Redo to avoid need
for IF_LINT, or for the static var.  No need to xstrdup optarg.