Allow math --scale=max for maximum digits #5579
Description
math should have an easier way of showing the maximum digits possible for floating point numbers than increasing -s until you get an error (15 currently, which corresponds to FLT_DIG. This could perhaps go up a little bit if we decided to use long double - I plan to do this to tinyexpr.cpp).
The most straightforward thing would be just letting the user pass -1 for a scale that is limited only by precision.