[RFA] split up ui_printf, fix decfloat printing bugs

[Tom Tromey]

>>>>> "Doug" == Doug Evans <dje@google.com> writes:

Doug> I don't understand this code in ui_printf:
[...]
Doug> It makes no sense given that the format string is parsed into pieces.
Doug> Am I missing something?

I don't understand it either.
I also think it is wrong as-is.

Doug> Regression tested on amd64-linux.
Doug> Ok to check in?

Looks good to me.

Tom