message: move config header out of guarding
diff: #ifndef MFEM_CPARDISO
  #define MFEM_CPARDISO
  +#include "../config/config.hpp"
  +
  #ifdef MFEM_USE_MPI
  #ifdef MFEM_USE_MKL_CPARDISO
  -#include "../config/config.hpp"
  #include "mkl_cluster_sparse_solver.h"
  #include "operator.hpp"
  