community/openjdk7: security upgrade to 2.6.23 (7u281)

Release Notes: https://mail.openjdk.java.net/pipermail/distro-pkg-dev/2020-November/042375.html

This MR also re-adds the fix for CVE-2019-2745, which was removed from the last upgrade due to compile errors. Should also fix build with gcc 10 and disable generation of not needed javadoc, thus making the build faster.

blocks !13757 (merged)