Please review a small fix to address an omission in the command-line help output generated by `javadoc --help`.
The text that is generated is the same as that for javac, which incidentally,
uses the same mechanism to expand @files. -- Jon JBS: https://bugs.openjdk.java.net/browse/JDK-8243396 Webrev: http://cr.openjdk.java.net/~jjg/8243396/webrev.00/
