fix in TMath::KolmogorovTest the case when the two vectors are identical

 - clean up and simplify also the code 

  in the case of ties the results have been checked manually with R ks.test function


git-svn-id: http://root.cern.ch/svn/root/trunk@36584 27541ba8-7e3a-0410-8455-c3a389f83636