calc: function WEEKNUM seems not to conform to ODFF1.2

[Winfried Donkers]

Hi Eike,

> > I would like to change the behaviour of function WEEKNUM to conform to
> > ODFF1.2 [...]
> 
> We might
> get away with strictly complying with ODFF and generate an error for
> constraint cases if prominently mentioned in release notes that WEEKNUM
> changed. Users will have to change formulas then and we get angry mails and
> bug reports ;-)
> 
> The other [...] quite more complicated than the first solution and introducing
> interoperability problems.
> 
> Therefor I'd go with strict ODFF implementation.

I will work on strictly implementing ODFF for WEEKNUM and ISOWEEKNUM.
I don't know if I will find a way to produce an error message explaining to the user what exactly is wrong when opening old files with WEEKNUM in it.

Winfried