code: static String createTagString(String lang, String script, String region, String trailing) {
          return createTagString(lang, script, region, trailing, null);
      }
docs: Create a tag string from the supplied parameters.  The lang, script and region
  parameters may be null references.If the lang parameter is an empty string, the
  default value for an unknown language is written to the output buffer.
  
  @param lang The language tag to use.
  @param script The script tag to use.
  @param region The region tag to use.
  @param trailing Any trailing data to append to the new tag.
  @return The new String.