Version checks on Jenkins

Randall Wood <rhwood@...>

Some comments on the Version checks on Jenkins:

- JDK/JRE 9, 10, 12 are no longer supported, and are not the defaults in any environment I can find; I don’t think there is value in testing those versions.
- JDK/JRE 13 has a GA release. Perhaps we should test that version?
- The JDK 11 failures are due to JavaDoc failures loading external URLs from (I’m working on a reproducible case for a bug report to — for compelely building successfully on JDK 11, those external links will need to be disabled (the way the two links that fail on JDK 8 are currently disabled). Should I submit a PR to allow building on JDK 8 and JDK 11?