Fix $watch docs to correctly define when angular.equals is used

src/ng/rootScope.js

@@ -223,10 +223,14 @@ function $RootScopeProvider(){
        *   {@link ng.$rootScope.Scope#$digest $digest()} and should be idempotent.)
        * - The `listener` is called only when the value from the current `watchExpression` and the
        *   previous call to `watchExpression` are not equal (with the exception of the initial run,
-       *   see below). The inequality is determined according to
-       *   {@link angular.equals} function. To save the value of the object for later comparison,
-       *   the {@link angular.copy} function is used. It also means that watching complex options
-       *   will have adverse memory and performance implications.
+       *   see below). Inequality is determined according to reference inequality,
+       *   <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Comparison_Operators">
+       *   strict comparison</a> via the `!==` Javascript operator, unless `objectEquality == true`
+       *   (see next point)
+       * - When `objectEquality == true`, inequality of the `watchExpression` is determined
+       *   according to the {@link angular.equals} function. To save the value of the object for
+       *   later comparison, the {@link angular.copy} function is used. This therefore means that
+       *   watching complex objects will have adverse memory and performance implications.
        * - The watch `listener` may change the model, which may trigger other `listener`s to fire.
        *   This is achieved by rerunning the watchers until no changes are detected. The rerun
        *   iteration limit is 10 to prevent an infinite loop deadlock.