Pty mode code added so that sshd server can do remote echo, backspace
processing. etc and ssh.exe client does not have to do local echo. We
can enrich it in future for more features and allowing programs like
powershell to run interactive. Pty mode is central for interactive use
and will be built using Windows console instead of termios that
Linux/Unix uses.
pty and tty support was not enabled or working in the code. Without pty
support, ssh client was very non functional - e.g. openssh linux server
prompt would not come through. Now ssh client works much better in
interactive mode ( uses pty).
NoMachine did not finish coding child process ending detection logic.
Added the needed code so that child process handle is added to the
handles that WaitForMultipleObjects() waits for in nomachine select()
implementation in socket.c. Otherwise select() would be stuck in
read/write dectection even when the process of interest has exited.
ssh.exe client invoked underneath was not able to send password prompt
and read password from user as stdin and stdout handles were redirected
to sockets by sftp.exe ; stderr which is not redirected is used to show
prompt to users and data is read from console
