Here is a patch for win32 implementation of TThread.
 - Improves speed of a factor 10 in a heavy context switching
   threaded application (by using critical sections).
 - Added R__LOCKGUARD2(gROOTMutex) in TThreadTimer.
 - Added CINT deadlock workaround for WIN32 in TMutex :-\
 - Protected calls to gInterpreter->Execute() in TCanvas.
 - Added gSystem->Sleep(10) in tutorial threadsh1.C


git-svn-id: http://root.cern.ch/svn/root/trunk@18326 27541ba8-7e3a-0410-8455-c3a389f83636