[pg] Client.query now accepts Submittables

This commit creates a new interface on @types/pg called Submittable
following the description on node-postgres API doc, which says:

> client.query with a Submittable
>
> If you pass an object to client.query and the object has a .submit
> function on it, the client will pass it's PostgreSQL server connection
> to the object and delegate query dispatching to the supplied object
> [...]

and uses the new interface as argument type to Client.query and
Pool.query. This allows the usage of pg-copy-streams package.

types/pg-query-stream/index.d.ts

@@ -6,6 +6,7 @@
 /// <reference types="node" />
 
 import stream = require("stream");
+import pg = require("pg");
 
 declare namespace QueryStream {
     interface Options {
@@ -14,11 +15,12 @@ declare namespace QueryStream {
     }
 }
 
-declare class QueryStream extends stream.Readable {
+declare class QueryStream extends stream.Readable implements pg.Submittable {
     batchSize: number;
     text: string;
     values?: any[];
     constructor(text: string, values?: any[], options?: QueryStream.Options);
+    submit(connection: pg.Connection): void;
 }
 
 export = QueryStream;

types/pg/index.d.ts

@@ -51,6 +51,10 @@ export interface QueryConfig {
     values?: any[];
 }
 
+export interface Submittable {
+    submit: (connection: Connection) => void;
+}
+
 export interface QueryArrayConfig extends QueryConfig {
     rowMode: 'array';
 }
@@ -148,7 +152,7 @@ export class Pool extends events.EventEmitter {
     end(): Promise<void>;
     end(callback: () => void): void;
 
-    query(queryStream: QueryConfig & stream.Readable): stream.Readable;
+    query<T extends Submittable>(queryStream: T): T;
     query(queryConfig: QueryArrayConfig): Promise<QueryArrayResult>;
     query(queryConfig: QueryConfig): Promise<QueryResult>;
     query(queryTextOrConfig: string | QueryConfig, values?: any[]): Promise<QueryResult>;
@@ -166,7 +170,7 @@ export class ClientBase extends events.EventEmitter {
     connect(): Promise<void>;
     connect(callback: (err: Error) => void): void;
 
-    query(queryStream: QueryConfig & stream.Readable): stream.Readable;
+    query<T extends Submittable>(queryStream: T): T;
     query(queryConfig: QueryArrayConfig): Promise<QueryArrayResult>;
     query(queryConfig: QueryConfig): Promise<QueryResult>;
     query(queryTextOrConfig: string | QueryConfig, values?: any[]): Promise<QueryResult>;