message: Ask NumPy for read only array when converting it to Tensor.
  Fix for:
  If numpy array is read-only, calling PyArray_FromAny with NPY_ARRAY_CARRAY
  flags introduce extra memory copy.
  Before:
  feed_cpu_variable_read_only: 5.6 GB/sec, min: 17.99, median: 19.54, mean: 19.76
  After:
  feed_cpu_variable_read_only: 13.2 GB/sec, min: 7.60, median: 7.78, mean: 8.13
diff: @@ -411,7 +411,7 @@ Status PyArrayToTF_Tensor(PyObject* ndarray, Safe_TF_TensorPtr* out_tensor) {
  // Make sure we dereference this array object in case of error, etc.
  Safe_PyObjectPtr array_safe(make_safe(
  - PyArray_FromAny(ndarray, nullptr, 0, 0, NPY_ARRAY_CARRAY, nullptr)));
  + PyArray_FromAny(ndarray, nullptr, 0, 0, NPY_ARRAY_CARRAY_RO, nullptr)));
  if (!array_safe) return errors::InvalidArgument("Not a ndarray.");
  PyArrayObject* array = reinterpret_cast<PyArrayObject*>(array_safe.get());
  