(cherry picked from v5-34-00-patches
 commit b91fea57)

(cherry picked from v5-34-00-patches
 commit 4188e406)

Fix for building with xrootd. The FindXROOTD.cmake has been simplied and a single variable XRROTD_INCLUDE_DIRS returns the normal and private include dirs. The clients packages in ROOT proof, netx and proofx have been adapted.

Fix a memory leak in assignment operator. The functions objects in the list of functions were not deleted

Add unused routines in order to suppress the error message:

include/RooTreeData.h:33:10: error: private field '_tree' is not used [-Werror,-Wunused-private-field]
  TTree *_tree ;           // TTree holding the data points
         ^

When creating mergers, the code iterates over all slaves to figure out how
many workers should be assigned to each merger. This is usually fine,
unless not all are active. In that situation it creates mergers that wait
forever (or almost forever) for workers which will never connect, which
obviously screws up the job. The fix changes the merger creation to iterate
over fActiveSlaves instead of fSlaves.

[From B.Butler, M.Swiatlowski]

TString is missing a newline; will refactor printing of delims (to be done by pcaller).