This lets us get rid of Xalan safely (as well as other often problematic
dependencies like nekohtml + Xerces combo), and reduce the dependency
footprint.

don't wake up so often when waiting for Jenkins to finish - it make take away to much time from the threads that are actually doing something

[JENKINS-11416] Added comment describing the motivation of the change. The real fix is in: ccdbd834

Adding the ant-launcher jar to the maven plugin.  On my environment without it gmaven is unable to locate the org.apache.tools.ant.launch.AntMain class

[JENKINS-11458] Channel.current() is only available from the thread that's executing the remote call, and that's why we saw this original error, when Maven uses a thread pool to call into this method from another worker thread.