fdo#74345: Minimalistic test to reproduce this.

Change-Id: Ibaa25f974ff98a8a601acbab25041b16d3b8dee2
fdo#74345: Some shared formulas cannot be exported as shared formulas.

Excel's shared formula has some restrictions that Calc's doesn't have.
So we need to check each shared formula token to see if we can export
it as shared when saving to Excel.  Refer to the "SharedParsedFormula"
section of the [MS-XLS] spec.

Change-Id: I0ffce26700d2773bbd2893743edc6c03682c2ed7