Interface to the C implementation of Ryu from:
https://github.com/ulfjack/ryu/tree/master/ryu.

There's no need to download that Ryu implementation as the
pertinent bits of it are already included in this module's source.

The files d2fixed.c and ryu_headers/generic_128.h (which are
part of the aforementioned C implemenation of Ryu) have received
some superficial modifications to cater for perl builds that do not
honor"C99 mode".

This implementation is not currently usable with perl builds whose
$Config{nvsize} > 8.

Otherwise, you can build with:

$ cpan -i Math::Ryu