Small fix to convertToFes where ceil was used instead of round

src/gridtools/GridVessel.cpp

@@ -97,7 +97,7 @@ void GridVessel::setBounds( const std::vector<std::string>& smin, const std::vec
     if( spacing.size()==dimension && binsin.size()==dimension ) {
       if( spacing[i]==0 ) nbin[i] = binsin[i];
       else {
-        double range = max[i] - min[i]; nbin[i] = std::ceil( range / spacing[i]);
+        double range = max[i] - min[i]; nbin[i] = std::round( range / spacing[i]);
         // This check ensures that nbins is set correctly if spacing is set the same as the number of bins
         if( nbin[i]!=binsin[i] ) plumed_merror("mismatch between input spacing and input number of bins");
       }