code: public void copyDocFiles(Configuration configuration, PackageDoc pd) {
          Location locn = configuration.getLocationForPackage(pd);
          copyDocFiles(configuration, locn, DocPath.forPackage(pd).resolve(DocPaths.DOC_FILES));
      }
docs: Copy the given directory contents from the source package directory
  to the generated documentation directory. For example for a package
  java.lang this method find out the source location of the package using
  {@link SourcePath} and if given directory is found in the source
  directory structure, copy the entire directory, to the generated
  documentation hierarchy.
  
  @param configuration The configuration of the current doclet.
  @param path The relative path to the directory to be copied.
  @param dir The original directory name to copy from.
  @param overwrite Overwrite files if true.