This ptg indicates a data table.
It only occurs in a FORMULA record, never in an
ARRAY or NAME record. When ptgTbl occurs in a
formula, it is the only token in the formula.
This indicates that the cell containing the
formula is an interior cell in a data table;
the table description is found in a TABLE
record. Rows and columns which contain input
values to be substituted in the table do
not contain ptgTbl.
See page 811 of the june 08 binary docs.
Overridden toString method to ensure object hash is not printed.
This helps get rid of gratuitous diffs when comparing two dumps
Subclasses may output more relevant information by overriding this method