Allows extending ActiveXObject with with specialized overloads returning string types, per #2541.

Author: zspitz

src/lib/scriptHost.d.ts

@@ -4,7 +4,11 @@
 /// Windows Script Host APIS
 /////////////////////////////
 
-declare var ActiveXObject: { new (s: string): any; };
+
+interface ActiveXObject {
+    new (s: string): any;
+}
+declare var ActiveXObject: ActiveXObject;
 
 interface ITextWriter {
     Write(s: string): void;