Use xstream 1.4.16 (#5360)

Changelog: https://x-stream.github.io/changes.html#1.4.16

Switches default parser to a fork of Xpp3 instead of using Xpp3 directly.
Resolves security vulnerabilities when unmarshalling with an XStream
instances using an uninitialized security framework.  As far as I
understand it, Jenkins is not susceptible to those vulnerabilities
because it initializes the security framework.

Also fixes two minor items:

* faulty XmlFriendlyNameCoder optimization
  https://github.com/x-stream/xstream/issues/237

* enum dereferences fail from older versions
  https://github.com/x-stream/xstream/issues/238