PseudoTerminal class

As a follow up to yesterday's post I did the "hard work" of cut-and-pasting the VTE pseudo-terminal support+gnome-pty-helper into an independent module and wrote a managed binding for the code, autoconf-ified it and put it on SVN.

Code lives in the pty-sharp module, or you can get a tarball.

Now someone needs to do the trivial hack of writing the Mono terminal emulator.