Cygwin: console: Fix issues of apps which open pty.

Cygwin: console: Fix issues of apps which open pty.

- After some recent changes for special keys handling break the
  apps which open pty (such as script command). If the app which
  opens pty is executed in console, the following issues occur.
    1) If the script command was started from non-cygwin shell
       (such as cmd.exe), another cygwin app started in pty slave
       cannot receive Ctrl-C.
    2) If non-cygwin app is executed in pty slave, the app which
       opened the pty (e.g. script command) crashes by Ctrl-C.
  This patch fixes these issues.