Node.js: ServerRequest.destroy() implemented.

This closes #871 issue on GitHub.

src/nodejs/unit-http/http_server.js

@@ -33,8 +33,17 @@ ServerResponse.prototype.statusMessage = undefined;
 ServerResponse.prototype.headers_len = 0;
 ServerResponse.prototype.headers_count = 0;
 ServerResponse.prototype.headersSent = false;
+ServerResponse.prototype.destroyed = false;
 ServerResponse.prototype.finished = false;
 
+ServerResponse.prototype.destroy = function destroy(error) {
+    if (!this.destroyed) {
+        this.destroyed = true;
+    }
+
+    return this;
+};
+
 ServerResponse.prototype._finish = function _finish() {
     this.headers = {};
     this.headers_len = 0;