nonpareil-0.79 and HP41 modules

[Albert Chan]

Hi hmilz,

I am happy that https://github.com/achan001/MAPM-5 got used in your project.

Just a comment on conversion from MAPM number to integer.
https://github.com/hmilz/hp-99/blob/main/hp-99.ino#L727

Quote:// sadly, there is no function to convert MAPM to int directly.
// alternative:
// i = (int) sto[i].toDouble(); // converts to double and casts to int.

Actually, "alternative" is much faster than doing MAPM -> string -> int.

m_apm_to_double(x) is fast, *and* with correct rounding.