math/sprng: make fetchable again with a silent update

The tarball for SPRNG 5.0 has been rerolled.
This includes several minor points:

• format change (dos to unix);
• code reformat and linting;
• code cleaning;

but also some other modifications.

Full diff available at https://people.freebsd.org/~thierry/sprng5.diff .

PR: 293802
Reported by: Daniel Engberg