message: ENH: use constexpr when possible
diff: @@ -819,7 +819,7 @@ void check_interp( double TOL=1.e-9 )
  //------------------------------------------------------------------------------
  TEST( mint_single_fe, check_override_max_newton )
  {
  - const int MAX_NEWTON = 42; // test value to override max newton
  + constexpr int MAX_NEWTON = 42; // test value to override max newton
  // STEP 0: construct a mesh with a single element
  mint::FiniteElement* fe = nullptr;
  @@ -839,9 +839,9 @@ TEST( mint_single_fe, check_override_max_newton )
  TEST( mint_fem_single_fe, matrix_constructor_deepcopy )
  {
  // STEP 0: constants used in the test
  - const int NROWS = 2;
  - const int NCOLS = 3;
  - const int NSIZE = NROWS * NCOLS;
  + constexpr int NROWS = 2;
  + constexpr int NCOLS = 3;
  + constexpr int NSIZE = NROWS * NCOLS;
  // STEP 1: setup element coordinates matrix
  numerics::Matrix< double > M( NROWS, NCOLS );
  @@ -880,9 +880,9 @@ TEST( mint_fem_single_fe, matrix_constructor_deepcopy )
  TEST( mint_fem_single_fe, matrix_constructor_shallowcopy)
  {
  // STEP 0: constants used in the test
  - const int NROWS = 2;
  - const int NCOLS = 3;
  - const int NSIZE = NROWS * NCOLS;
  + constexpr int NROWS = 2;
  + constexpr int NCOLS = 3;
  + constexpr int NSIZE = NROWS * NCOLS;
  // STEP 1: setup element coordinates matrix
  numerics::Matrix< double > M( 2, 3 );
  