Upgrade libraries to new Debian stable
The new Debian stable is out, and we should upgrade our library versions to use what's contained in there.
Note that it might still take a while until hosts will be running Debian stable. But we only depend on Java 7 (soon 8) there. If we build locally with newer library versions, it shouldn't matter whether hosts are running jessie or stretch.
Putting this on high priority, because our Jenkins metrics-lib builds are currently failing, because they're running stretch, not jessie. We could temporarily disable them, but we could as well to this upgrade now.