Fix OPOST for non-Cygwin pty slaves

Fix OPOST for non-Cygwin pty slaves

	* fhandler.h (class fhandler_base): Add virtual function
	get_io_handle_cyg() to get handle from which OPOST-processed output is
	read on PTY master.
	(class fhandler_pty_slave): Add variable output_handle_cyg to store a
	handle to which OPOST-processed output is written. Add two functions,
	i.e., set_output_handle_cyg() and get_output_handle_cyg(), regarding
	variable output_handle_cyg. Now, output_handle is used only by native
	windows program. The data before OPOST-processing is written to
	output_handle and OPOST-processing is applied in the master-side. For a
	cygwin process, OPOST-processing is applied in the slave-side, and the
	data after OPOST-processing is written to output_handle_cyg.
	(class fhandler_pty_master): Add two variables, i.e., io_handle_cyg and
	to_master_cyg, to store handles of a pipe through which OPOST-processed
	output passes. Add pty_master_fwd_thread and function
	pty_master_fwd_thread() for a thread which applies OPOST-processing
	and forwards data from io_handle to to_master_cyg. Add function
	get_io_handle_cyg() regarding variable io_handle_cyg. Now, the pipe
	between io_handle and to_master are used only by native windows program
	for applying OPOST-processing in the master-side. For a cygwin process,
	the pipe between io_handle_cyg and to_master_cyg is used for passing
	through the data which is applied OPOST-processing in the slave-side.
	* fhandler_tty.cc (struct pipe_reply): Add member to_master_cyg.
	(fhandler_pty_master::process_slave_output): Read slave output from
	io_handle_cyg rather than io_handle.
	(fhandler_pty_slave::fhandler_pty_salve): Initialize output_handle_cyg.
	(fhandler_pty_slave::open): Set output_handle_cyg by duplicating handle
	to_master_cyg on PTY master.
	(fhandler_pty_slave::close): Close handle output_handle_cyg.
	(fhandler_pty_slave::write): Write data to output_handle_cyg rather
	than output_handle.
	(fhandler_pty_slave::fch_close_handles): Close handle output_handle_cyg.
	(fhandler_pty_master::fhandler_pty_master): Initialize io_handle_cyg,
	to_master_cyg and master_fwd_thread.
	(fhandler_pty_master::cleanup): Clean up to_master_cyg as well.
	(fhandler_pty_master::close): Print to_master_cyg as well in debug
	message. Terminate master forwarding thread. Close handles
	to_master_cyg and io_handle_cyg.
	(fhandler_pty_master::ioctl): Use io_handle_cyg rather than to_master.
	(fhandler_pty_master::pty_master_thread): Add code for duplicating
	handle to_master_cyg.
	(fhandler_pty_master::pty_master_fwd_thread): New function for a thread
	to forward OPOST-processed data from io_handle to to_master_cyg.  This
	thread applies OPOST-processing to the output of native windows program.
	(::pty_master_fwd_thread): Ditto.
	(fhandler_pty_master::setup): Create a new pipe to pass thruegh OPOST-
	processed output. Create new thread to forward data from io_handle to
	to_master_cyg. Set handle to_master_cyg to tty. Print io_handle_cyg as
	well in debug message. Close handles io_handle_cyg and to_master_cyg in
	case of error.
	(fhandler_pty_master::fixup_after_fork): Set handle to_master_cyg to
	tty. Copy handle to_master_cyg from arch->to_master_cyg.
	(fhandler_pty_master::fixup_after_exec): Clean up to_master_cyg.
	* select.cc: Check handle returned by get_io_handle_cyg() rather than
	get_handle().
	* tty.h (class tty): Add variable _to_master_cyg to store a handle to
	which OPOST-processed data is written. Add two functions,
	to_master_cyg() and set_to_master_cyg(), regarding _to_master_cyg.

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>