7059905: (javadoc) promote method visibility for netbeans usage

Reviewed-by: jjg, bpatel

langtools/src/share/classes/com/sun/tools/javadoc/DocImpl.java

@@ -92,7 +92,7 @@ public abstract class DocImpl implements Doc, Comparable<Object> {
      * So subclasses have the option to do lazy initialization of
      * "documentation" string.
      */
-    String documentation() {
+    protected String documentation() {
         if (documentation == null) documentation = "";
         return documentation;
     }