make vscode.d.ts use a declare module, #13990

* a declared module allows to have a sibling module containing experimental API
* this change also cleans up some bogous type pollution that happened because vscode used to be both, a declare module and a global namespace

src/vs/workbench/api/node/extHostOutputService.ts

@@ -6,6 +6,7 @@
 
 import { IThreadService } from 'vs/workbench/services/thread/common/threadService';
 import { MainContext, MainThreadOutputServiceShape } from './extHost.protocol';
+import * as vscode from 'vscode';
 
 export class ExtHostOutputChannel implements vscode.OutputChannel {