Mark getSynthesizedDeepClone @internal

src/compiler/factory.ts

@@ -74,6 +74,7 @@ namespace ts {
     /**
      * Creates a deep, memberwise clone of a node with no source map location.
      */
+    /* @internal */
     export function getSynthesizedDeepClone<T extends Node>(node: T | undefined): T | undefined {
         return node
             ? getSynthesizedClone(visitEachChild(node, child => getSynthesizedDeepClone(child), nullTransformationContext))