printf has a nice feature that let us print big numbers as "1,234.12". We make this available also Cuis printf.
in printf the modifier is $' , i don't want to use that in Cuis because it is our one and only literal string delimiter, so i use $_ as modifier i.e. %d thousand separated is %_d, and %0.2f thousand separated would be %_0.2f
I use _ as default thousand separator in agreement with what Perl, Ruby and recently also Python accept.
The user has possibility of deciding his own thousand and decimal separator. Indeed in Italy for example we would print financial values as e.g. 1,234.12 .
new tests are added
new tests are kept separated from the old ones, they are progressively numbered
Detected bug in existing Printf code, made test to keep it in sight and remember it is there. It is an ugly bug on printing big values. see test101_X .