Handling of worksheet functions from Excel 2010 and newer

[Winfried Donkers]

Hi Markus, Kohei, Eike,

>Kohei added the tests with http://cgit.freedesktop.org/libreoffice/core/commit/sc/qa?id=c40cbf189750f623e065b6ed9596d90977a2f631 
>but at least IMO it makes more sense to add test cases similar to testFunctionODS just for XLSX where you add corner cases for new functions. 
>I suppose that you already have a set of corner cases for your tests and you can just use these for the import and export tests.

The tests Kohei added are of some functions I recently added (plus one that I'm still working on), so I will expand both the xlsx-file and the ScFiltersTest::testFunctionsExcel2010().
(The xlsx-file will have to checked by someone with Excel though, before getting pushed. I don't have Excel)

Winfried