make now consistent with original Fortran code 
(available at Phystat : https://plone4.fnal.gov/P0/phystat/packages/0707001/1.1.0/view )


git-svn-id: http://root.cern.ch/svn/root/trunk@23481 27541ba8-7e3a-0410-8455-c3a389f83636