Move private APIs to private namespace

Fixes #2078

src/core/CallTracker.js

@@ -123,7 +123,9 @@ getJasmineRequireObj().CallTracker = function(j$) {
      * @param {Function} [argsCloner] A function to use to clone the arguments. Defaults to a shallow cloning function.
      * @function
      */
-    this.saveArgumentsByValue = function(argsCloner = j$.util.cloneArgs) {
+    this.saveArgumentsByValue = function(
+      argsCloner = j$.private.util.cloneArgs
+    ) {
       opts.cloneArgs = true;
       opts.argsCloner = argsCloner;
     };