make plotOn taking a RooLinkedList public

Signed-off-by: Wouter Verkerke <verkerke@nikhef.nl>
BidirMMapPipe: make the shutdown sequence for pipes and socketpairs more similar

This patch makes the shutdown sequences for pipes and socketpairs more
similar, and should in fact be more robust under high load.

Signed-off-by: Wouter Verkerke <verkerke@nikhef.nl>
fix race condition between dirty shutdown of BidirMMapPipe and RooRealMPFE

When a RooRealMPFE is not deallocated at runtime, but has it's
destructor called during after main() has exited, it may happen that the
cleanup routines for BidirMMapPipe are called first by the C++ runtime
shutdown code. In that case, the pipe held by RooRealMPFE is already
closed by the time RooRealMPFE tries to send the regular Terminate
message to the child process. The patch detects this, and refrains from
sending this final message over the pipe, since the child is no longer
alive at that point. Since the parent process is not waiting for any
data from the child, this is not harmful.

Signed-off-by: Wouter Verkerke <verkerke@nikhef.nl>
  Update stressRooStats reference file. When I run stressRooStats with the ref file from the patches branch it runs
  fine, except two two tests, which are not configured to run in the patches branch, but do exist in the master.
  Thus I have regenerated the reference file to complete it for the master with new reference data for the missing
  tests.

  I also import some very small changes in the tests from the patches branch