Missing updatestats (#351)

* aligning screeninit with pxt32

* remove shim

* missing shim

* missing shim

sim/state/screen.ts

@@ -98,3 +98,9 @@ namespace pxsim.image {
         return image.ofBuffer(res)
     }
 }
+
+namespace pxsim.pxtcore {
+    export function updateStats(str: string) {
+        // TODO
+    }
+}