Trac/1417 - add pseudoterminal support to the unix library

This is a very simple enhancement. openPseudoTerminal :: IO (Fd, Fd) getSlaveTerminalName :: Fd -> IO FilePath Here's the ticket: http://hackage.haskell.org/trac/ghc/ticket/1417 The code ought to work on Linux, Solaris, BSD, HP/UX, and Cygwin, too. I've compile-tested it on Linux, using both openpty and explicit open of /dev/ptmx. I propose a discussion period of one week. Thanks,