message: switch to T* Memory version so we can set own=false
  add const GetData
diff: @@ -962,13 +962,14 @@ public:
  DenseMatrix &operator()(int k)
  {
  MFEM_ASSERT_INDEX_IN_RANGE(k, 0, SizeK());
  - Mk.data = Memory<double>(tdata, SizeI()*SizeJ()*k, SizeI()*SizeJ());
  + Mk.data = Memory<double>(GetData(k), SizeI()*SizeJ(), false);
  return Mk;
  }
  const DenseMatrix &operator()(int k) const
  {
  MFEM_ASSERT_INDEX_IN_RANGE(k, 0, SizeK());
  - Mk.data = Memory<double>(tdata, SizeI()*SizeJ()*k, SizeI()*SizeJ());
  + Mk.data = Memory<double>(const_cast<double*>(GetData(k)), SizeI()*SizeJ(),
  + false);
  return Mk;
  }
  @@ -994,6 +995,12 @@ public:
  return tdata+k*Mk.Height()*Mk.Width();
  }
  + const double *GetData(int k) const
  + {
  + MFEM_ASSERT_INDEX_IN_RANGE(k, 0, SizeK());
  + return tdata+k*Mk.Height()*Mk.Width();
  + }
  +
  double *Data() { return tdata; }
  const double *Data() const { return tdata; }
  