mistyped %disconnect function overwriting %unbind

Found this bug while trying to call disconnect.  My push's and pull's were going through but i was getting an error about %disconnect not being defined.  I tracked it down and saw that unbind/disconnect had become conflated in the ffi file.  Fixing this caused the lisp error to go away, but also caused my messages to stop going through.  When I removed the (now functioning) disconnect, my messages resumed flowing.  Obviously I dont understand something about zmq.  

Either way, this changed definitely prevents a lisp error on calling disconnect.