Per https://doc.rust-lang.org/reference.html#fn2, non-ASCII characters are currently not allowed in stable Rust, so keep it ASCII-only for now. Signed-off-by: Dirkjan Ochtman <dirkjan@ochtman.nl>
With tweaks from Andrea Canciani, Ben Young, Tennix, and Dirkjan Ochtman. This fulfills https://savannah.gnu.org/bugs/?48163.