Automatize running of PROOF sessions in valgrind.
   The second argument of TProof::Open is used to trigger the relevant settings.

   To valgrind the master session start PROOF with

      TProof::Open("<master>","valgrind")

   or

      TProof::Open("<master>","valgrind=master")

   To valgrind two workers sessions use

      TProof::Open("<master>","valgrind=workers")

   To valgrind <n> workers sessions use

      TProof::Open("<master>","valgrind=workers#<n>")


   To valgrind master and 2 workers (for <n> workers add '#<n>')

      TProof::Open("<master>","valgrind=master+workers")


   The valgrind logs are available with the tag '<ordinal>-valgrind' in the log dialog
   or form TProofMgr::GetSessionLogs() .

   To add options to valgrind execute

      TProof::AddEnvVar("PROOF_WRAPPERCMD", "valgrind_opts:<options>")

   before starting the session.


git-svn-id: http://root.cern.ch/svn/root/trunk@29059 27541ba8-7e3a-0410-8455-c3a389f83636