ArrayPtg - handles arrays
The ArrayPtg is a little wierd, the size of the Ptg when parsing initially only
includes the Ptg sid and the reserved bytes. The next Ptg in the expression then follows.
It is only after the "size" of all the Ptgs is met, that the ArrayPtg data is actually
held after this. So Ptg.createParsedExpression keeps track of the number of
ArrayPtg elements and need to parse the data upto the FORMULA record size.