Changes motivated by these pedantic warnings:

/home/ed/pism/src/base/iMfractures.cc: In member function ‘virtual PetscErrorCode IceModel::calculateFractureDensity()’:
/home/ed/pism/src/base/iMfractures.cc:205:24: warning: variable ‘sigmabetanull’ set but not used [-Wunused-but-set-variable]
           KSI, KSImax, sigmabetanull, sigmatetanull;
                        ^

/home/ed/pism/src/base/iMIO.cc: In member function ‘virtual PetscErrorCode IceModel::init_enthalpy(std::string, bool, int)’:
/home/ed/pism/src/base/iMIO.cc:602:68: warning: declaration of ‘regrid’ shadows a member of 'this' [-Wshadow]
                                        bool regrid, int last_record) {
                                                                    ^