Improve TMath::KolmogorovTest (Jason Detwiler)

//
//  Method Improvement by Jason A Detwiler (JADetwiler@lbl.gov)
//  -----------------------------------------------------------
//   The nuts-and-bolts of the TMath::KolmogorovTest() algorithm is a for-loop
//   over the two sorted arrays a and b representing empirical distribution
//   functions. The for-loop handles 3 cases: when the next points to be 
//   evaluated satisfy a>b, a<b, or a=b:
//    
//      for (Int_t i=0;i<na+nb;i++) {
//         if (a[ia-1] < b[ib-1]) {
//            rdiff -= sa;
//            ia++;
//            if (ia > na) {ok = kTRUE; break;}
//         } else if (a[ia-1] > b[ib-1]) {
//            rdiff += sb;
//            ib++;
//            if (ib > nb) {ok = kTRUE; break;}
//         } else {
//            rdiff += sb - sa;
//            ia++;
//            ib++;
//            if (ia > na) {ok = kTRUE; break;}
//            if (ib > nb) {ok = kTRUE; break;}
//        }
//         rdmax = TMath::Max(rdmax,TMath::Abs(rdiff));
//      }
//    
//   For the last case, a=b, the algorithm advances each array by one index in an
//   attempt to move through the equality. However, this is incorrect when one or
//   the other of a or b (or both) have a repeated value, call it x. For the KS
//   statistic to be computed properly, rdiff needs to be calculated after all of
//   the a and b at x have been tallied (this is due to the definition of the
//   empirical distribution function; another way to convince yourself that the
//   old CERNLIB method is wrong is that it implies that the function defined as the
//   difference between a and b is multi-valued at x -- besides being ugly, this
//   would invalidate Kolmogorov's theorem).
//    
//   The solution is to just add while-loops into the equality-case handling to
//   perform the tally:
//    
//         } else {
//            double x = a[ia-1];
//            while(a[ia-1] == x && ia <= na) {
//              rdiff -= sa;
//              ia++;
//            }
//            while(b[ib-1] == x && ib <= nb) {
//              rdiff += sb;
//              ib++;
//            }
//            if (ia > na) {ok = kTRUE; break;}
//            if (ib > nb) {ok = kTRUE; break;}
//         }


git-svn-id: http://root.cern.ch/svn/root/trunk@21031 27541ba8-7e3a-0410-8455-c3a389f83636