Add support for auto linking javadoc on spec api reference

Any text of style java(x).something.SomeClass will be auto linked
to the official published JavaDoc page.

NOTE:
 Based on custom patched Asciidcotor branch

REF:
 https://github.com/asciidoctor/asciidoctor/pull/982
 https://github.com/asciidoctor/asciidoctor/pull/983