[Rd] Rust bindings to nmath

[Richard Dodd]

Hello @R-devel

I needed some statistical functions for a project I was working on in
Rust, and I've used the R math library as a standalone solution. I
thought the R developers would be interested in the fact that their work
is being used elsewhere, and I also wanted to say thanks for some code I
do NOT want to have to write myself!

The "crate" (Rust's name for a package) is at 
https://lib.rs/crates/r_stats.

Best wishes
Richard Dodd