Since JDK 11, javadoc's package-list file is superseded by element-list file, but a lot of external tools still need it. This PR makes a workaround by manually copying element-list file to package-list file.
Downgrade javadoc to html4 When we upgraded build JDK to 11, javadoc html was upgrade to html 5 by default. However, Docbook complaint and some DSL documentations was broken. Now we downgrade to html 4 by adding -html4 option to javadoc task.