The patch implements the following new functionality:

  - Shutdown of idle sessions when quitting ROOT; if not idle the session
    is shutdown as soon as processing terminates; it is possible to delay
    the automatic shutdown by a tunable amount of time via a new directive
    in the xrootd config file 'xpd.shutdown' (see xpd.cf.example).

  - New static method TProof::Reset(const char *url) to hard-cleanup an
    user area (implemented for Xproofd only); this implied quite some
    additions in XrdProofdProtocol.

  - Possibility to temporary remove / re-insert a worker from the active list
       TProof::DeactivateWorker(const char *ord)
       TProof::ActivateWorker(const char *ord)
    with 'ord' the ordinal numer, e.g. "0.3" .

  - A default url for the disk pool
       const char *TVirtualProof::GetDataPoolUrl()
    It is set by default to a string send back by the master, but it can
    be changed via
       void  TVirtualProof::SetDataPoolUrl(const char *url)

    Jan should then adapt his code to use this as default.

  - Posibility to timeout Collect; for now this is only used at forced
    termination.

The patch includes many small changes and bug fixes. One of the most important
is in TXNetSystem (a bug preventing correct treatment of multiple request
to the same redirector).


git-svn-id: http://root.cern.ch/svn/root/trunk@15507 27541ba8-7e3a-0410-8455-c3a389f83636