Dec() results not switching to fixed decimal format

[Jason Jorgensen]

In v0.11 the dec() function would correctly display a hex number converted to decimal. In version 0.12 the display of the converted hex number will always display in exponential notation.

v0.12: dec(0xea5d6800) =3.931990016e9

v0.11: dec(0xea5d6800) =3931990016

[Helder Correia]

Nothing to do with hex in particular, since also dec(3931990016) = 3,931990016e9 even in Fixed Decimal result format. This is indeed a regression, but I couldn't find out the responsible commit via git bisect, since builds become very dificult when going back in time closer to 0.11 due to all the changes in Qt/CMake/doc requirements. This needs to be debugged by hand. @teyut @polwel please let me know if you have a clue where this might have gotten broken.

[Pol Welter]

I have a hunch that it is related to 5658894. There I fixed an issue that very closely resembles this for bin, hex and oct, but not dec. Maybe we just need to add the same thing for dec.

[Tey']

Fixed in 2626c49: format.base was set by dec/hex/oct/bin functions but not format.mode, and this case was not handled by NumberFormatter::format().