From Gerri:
This patch adds support for XrootD 3.3.1 (out today) and higher. It
disables xrootd if the version is 3.3.0 (missing headers).


git-svn-id: https://root.cern.ch/svn/root/branches/v5-34-00-patches@48831 27541ba8-7e3a-0410-8455-c3a389f83636