Attaching:
 - Find an fd corresponding to the tty in the child
 - Open the new pty in the child
 - Copy the termios settings over
 - dup() it over the old ones
 - Make the new tty the controlling tty:
  - Fork a dummy child
  - Find all processes in the child's process group.
   - For each one, move them to the dummy child's process group
  - Make the child setsid()
  - Set the terminal as the controlling tty
 - Close the newly allocated tty
 - Detach
