object contains only one variable.

Also check that the dseries object is not empty.

Do not use exist function, check the output of dir() instead.

Variable reorder_variables_in_c needs to be initialized to false.

Do not test the equality of dseries object but the equality of data
members instead.

Third test was only testing that a dseries object is equal to itself.

Try to determine the values of these dummy variables from the content of
the first line and the first column

Also, for people who don't have the IO package, always use the fallback
code (even when the first line is <= 4096 bytes long).

Ref #2