Revision 38227

  Add the possibility to access the files on the workers via the same port used
  by PROOF. This is useful for cases when it is not possible to start a file server
  daemon on a different port (because, for eample, of a firewall or just inconvenience)
  and workers do not share a file system.
  Internally this works by forking a 'rootd' after identifying a file request and
  trasferring the connection to it. The client side is a TNetFile and it is triggered
  by the protocol "rootd://" (the just implemented etc/plugins/TFile/P120_TNetFile.C
  includes this protocol).
  On the server-side this new service is disabled by default and requires the directive
  
       xpd.rootd allow

  to be active. By default the 'rootd' is started in 'read-only' mode and no authentication.
  This can be change with some switches supported by the directive; for example
 
       xpd.rootd allow auth:full mode:rw

  starts 'rootd' in 'read-write' mode and authentication controlled by etc/system.rootdaemonrc .
  The list of avaialbe switches is documented at

       http://root.cern.ch/drupal/content/configuration-reference-guide#rootd

  The directive 'xpd.rootdallow' can be used to define the list of hosts allowed to use
  this service: see

       http://root.cern.ch/drupal/content/configuration-reference-guide#rootdallow

  The default setting of the environment variable LOCALDATASERVER has been changed to be
  "rootd://<host>:<proof_port> if file-serving via 'rootd' is enabled. In this way 
  TProofOutputFile automatically sets the correct default URL for further access from the
  master or other workers.
  The can always be overwritten with a dedicated 'xpd.putenv LOCALDATASERVER=<my_setting>'
  directive .