add protection again gSystem disappearing at end of program before the last
thread is finished. There remains a problem with threads.cxx however, that
will be solved later.


git-svn-id: http://root.cern.ch/svn/root/trunk@21532 27541ba8-7e3a-0410-8455-c3a389f83636

make program work on Windows (TH1::Draw() is not thread safe).


git-svn-id: http://root.cern.ch/svn/root/trunk@14922 27541ba8-7e3a-0410-8455-c3a389f83636

git-svn-id: http://root.cern.ch/svn/root/trunk@10789 27541ba8-7e3a-0410-8455-c3a389f83636