(request_limit): New variable.
(start_writing): New static function.
(start_reading): Ditto.
(stop_reading): Ditto.
(read_stdin): New command: start-reading.
(read_server): If do_write_only, just return OOP_HALT when eof on
	the server is seen--don't print anything.  Print a message if
	more than request_limit replies are received.
(write_server): Made a log message unique.
(main): Use start_reading(), start_writing() and stop_reading() to
	simplify the code.  Don't do a final write; different Unixes
	handles this in various strange ways, and we don't want to
	test *them*.