killall - Add all-but-self tty kill (-T)

* Add a new feature to killall, the -T option, which will kill all
  processes on the caller's tty except processes which parent the
  killall.

  This can be used to terminate processes on the current tty, for example
  from a ^C'd build that failed to kill all the sub processes, without
  also taking out the shell/xterm/whatever and causing the window to close.