Fix: solve the problem of occasional crash with DGVM after several years of simulation (relevant modifications in : lpj_establish.f90, stomate_lpj.f90, hydrol.f90, constantes_mtc.f90)
Fix: turnover rate of soil carbon for crop PFTs: there was an acceleration of soil carbon turnover for crops if OK_PC=n, as well as in TRUNK, but not in the case of OK_PC=y. Now it's also added in the case OK_PC=y. It can be controlled by parameter "FLUX_TOT_COEFF" in run.def.
Fix: correct a debug about "tmc_layt" in thermosoil.f90 (ticket:366)
New: add an option to choose the method for soil thermal conductivity (controlled by flag "USE_SOILC_METHOD") and snow thermal conductivity (flag "SNOW_COND_METHOD"). For both flags, the default are the same as before this commit.
Done by Dan
