major formatted output function bug with %c and the value 0

[marco.bodrato at tutanota.com]

Ciao,

18 feb 2024, 12:29 da marco.bodrato at tutanota.com:

> 15 dic 2023, 13:26 da vincent at vinc17.net:
>
>> Note that there are similar issues in printf/repl-vsnprintf.c, and I
>>
>
> I finally had the time to examine the code and test it. I attach a proposed patch.
>
Vincent, you did not confirm that this code worked for you, but I pushed it anyway.
https://gmplib.org/repo/gmp/rev/4ac76064639e

Thanks.
m