unexpected behaviour whilst fixing fdo#50118

[Winfried Donkers]

Hi Eike,

>> It makes me wonder if this [mess] may have been the reason why long ago the add-in functions were excluded when changing the formula language...
> Changing formula language during runtime started as experimental, it probably was simply an oversight to not handle the Add-In functions.
I envy your memory ;)

>> And, consequently, if I shouldn't leave it with https://gerrit.libreoffice.org/#/c/6032/ ?
> I'll take a look again.

I did continue trying to make things work, but kept producing crashes (application terminations).
Problem I encounter are a.o.
-filling the list with function names is in ScUnoAddInCollection, refilling it is not yet possible and proves to be troublesome;
-ScDocShell::SetFormulaOptions is called when changing the setting 'use English function names' and is called on start up. In the first case I want to refill the list, in the second case the list needs to be filled yet. To cope with this, I had to introduce a static boolean bFirstCall, which does not look good to me.
I could show you the code I have produced so far, but I'm not confident I'm on the right track and I suggest I leave it for someone brighter than me.
(Unless you have some golden hints, of course.)

Winfried