Merge from vscode a234f13c45b40a0929777cb440ee011b7549eed2 (#8911)

* Merge from vscode a234f13c45b40a0929777cb440ee011b7549eed2

* update distro

* fix layering

* update distro

* fix tests

src/typings/lib.ie11_safe_es6.d.ts

@@ -12,7 +12,7 @@ interface Map<K, V> {
 	forEach(callbackfn: (value: V, index: K, map: Map<K, V>) => void, thisArg?: any): void;
 	get(key: K): V | undefined;
 	has(key: K): boolean;
-	set(key: K, value?: V): Map<K, V>;
+	set(key: K, value: V): Map<K, V>;
 	readonly size: number;
 
 	// not supported on IE11:

src/typings/require.d.ts

@@ -31,7 +31,7 @@ declare class LoaderEvent {
 	readonly detail: string;
 }
 
-declare var define: {
+declare const define: {
 	(moduleName: string, dependencies: string[], callback: (...args: any[]) => any): any;
 	(moduleName: string, dependencies: string[], definition: any): any;
 	(moduleName: string, callback: (...args: any[]) => any): any;