In TPacketizerUnit, add the possibility to exactly share the number of cycles between
   the workers. This functionality was triggered by a request from roostat and it can be
   useful when this packetizer is used to perform well defined actions on the workers.
   The option can be enabled by calling
           proof->SetParameter("PROOF_PacketizerFixedNum", (Int_t)1)
   before processing.


git-svn-id: http://root.cern.ch/svn/root/trunk@34086 27541ba8-7e3a-0410-8455-c3a389f83636