Checks only the ENTRY and TGROUP elements,
the first to find the column number, and the second to find the total
number of columns.
Node we want the column number of.
If this is not an ENTRY element, then the column number will be
returned as zero.
Type: list of numbers
A list of numbers, where
the car is the current column number,
and the cadr is the total number of columns.
If the argument is not for an ENTRY element,
then the current column number will be returned as zero.
If the node doesn't have a TABLE in its ancestry,
then return #f.