After adding a warning for `{@link}` tags that refer to private/protected types, we see these warnings when building javadoc.


```
src/jdk.jshell/share/classes/jdk/jshell/Snippet.java:527: warning: reference to non-visible type: SnippetEvent.previousStatus (use -protected or -private options to document non-public types)
         * Used only in {@link SnippetEvent#previousStatus} for new
                        ^

src/jdk.jshell/share/classes/jdk/jshell/SourceCodeAnalysis.java:153: warning: reference to non-visible type: JShell.eval (use -protected or -private options to document non-public types)
     * Restrictions on the input are as in {@link JShell#eval}.
                                           ^

```