pty implementation for go
pty implementation for go

Largely adapted from
https://github.com/chjj/pty.js/blob/master/src/unix/pty.cc
http://exbb.fsay.net/shell/term-ws/ws.go

control-center/serviced,control-center/serviced,control-center/serviced,control-center/serviced,control-center/serviced,control-center/serviced,control-center/serviced,control-center/serviced