Add zlib option finishFlush (#11731)

See
https://nodejs.org/dist/latest-v6.x/docs/api/zlib.html#zlib_class_options

node/index.d.ts

@@ -1026,7 +1026,7 @@ declare module "cluster" {
 
 declare module "zlib" {
     import * as stream from "stream";
-    export interface ZlibOptions { chunkSize?: number; windowBits?: number; level?: number; memLevel?: number; strategy?: number; dictionary?: any; }
+    export interface ZlibOptions { chunkSize?: number; windowBits?: number; level?: number; memLevel?: number; strategy?: number; dictionary?: any; finishFlush?: number }
 
     export interface Gzip extends stream.Transform { }
     export interface Gunzip extends stream.Transform { }

node/node-tests.ts

@@ -421,7 +421,7 @@ namespace util_tests {
 // http://nodejs.org/api/stream.html#stream_readable_pipe_destination_options
 function stream_readable_pipe_test() {
     var r = fs.createReadStream('file.txt');
-    var z = zlib.createGzip();
+    var z = zlib.createGzip({ finishFlush: zlib.Z_FINISH });
     var w = fs.createWriteStream('file.txt.gz');
     r.pipe(z).pipe(w);
     r.close();