Rounding issue in GR6J UH stores

In some cases (low flows) the values stored in UH are returned very negative by the GR6J Fortran code. This causes an error message in RunModel_CemaNeigeGR6J when the final state is created by the CreateIniStates function, since there is a check to avoid negative values in UH. This is probably due to rounding in the Fortran code.