Bug#822091: libxmlbeans-java: Embeds classes without source

[Emmanuel Bourg]

I got another look at this, and maybe it isn't as bad as we thought. The
piccolo jars in external/lib/ do not contain compiled .class files, but
only .java source files. The xmlbeans build unpacks them to
build/private/piccolo/src, changes the package to
org.apache.xmlbeans.impl.piccolo, and then compiles them.

There are still a few jar files with compiled classes (junit, saxon,
jsr173, oldxbean) but they aren't used to build the package. So this is
more a matter of cleaning the upstream tarball of unnecessary files than
fixing a severe policy violation.

Emmanuel Bourg