There was some nasty global-ish variable reference updating happening when the native module 'initializes' after its require with `require('pg').native`
This fixes the issue by making sure both `require('pg')` and `require('pg').native` each initialize their own context in isolation and no weird global-ish references are used & subsequently stomped on.
When a __prepared statement__ has no body in the query the backend responds with an `emptyQuery` message but never with a `commandComplete` or `errorResponse` message. The client was hanging forever waiting for one of the other two expected messages. The server was hanging forever waiting for the client to respond with a `sync` message. This change has the client send the required `sync` on receipt of an `emptyQuery` message when the query is a prepared statement. Fixes#822
