message: Make Vector::Normlp less prone to overflow
  Use a scaling trick (also performed in C++'s std::hypot) to prevent
  overflow of $\ell^{p}$ norm of `mfem::Vector`s in some cases (e.g.,
  large values of $p$).
diff: @@ -705,12 +705,21 @@ double Vector::Normlp(double p) const
  }
  if (p < std::numeric_limits<double>::infinity())
  {
  + // Scale entries of Vector by L-infinity norm to prevent overflow
  + // when taking entries to the pth power, which may occur when p
  + // is large and/or data[i] is large in absolute value for some
  + // valid value of i. Computing this scaling factor, performing
  + // the scaling, and then rescaling the result at the end of the
  + // computation costs n divisions and (n + 1) comparisons, but
  + // ensures that every exponentiated term in the summation has
  + // magnitude no greater than one.
  + const double inf_norm = Normlinf();
  double sum = 0.0;
  for (int i = 0; i < size; i++)
  {
  - sum += pow(fabs(data[i]), p);
  + sum += pow(fabs(data[i] / inf_norm), p);
  }
  - return pow(sum, 1.0/p);
  + return pow(sum, 1.0/p) * inf_norm;
  }
  else
  {
  