imported 1.4.4 from http://svn.codehaus.org/xstream/tags/XSTREAM_1_4_4/
merged 1.4.4
follow-up compilation error fix
resurrecting code lost during the merge.

Originaly change is in c37f7f5032880b0b08fb2f090faed8a2b9d9fc3b
Resurrected backward compatibility.

XStream now defines this in ExtendedHierarchicalStreamReader but
historically Jenkins defined this in HierarchicalStreamReader.

Fortunately, every known implementation of HierarchicalStreamReader
in XStream also implements ExtendedHierarchicalStreamReader, so this is
safe for us.
Lost this change during the merge

This was originally in 1c687806e48b423527b3dd82b15cc8a7e2f6911f